Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
  • B08B7/0021—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by liquid gases or supercritical fluids
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/50—Solvents
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L1/00—Dry-cleaning or washing fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D2111/00—Cleaning compositions characterised by the objects to be cleaned; Cleaning compositions characterised by non-standard cleaning or washing processes
  • C11D2111/10—Objects to be cleaned
  • C11D2111/14—Hard surfaces
  • C11D2111/20—Industrial or commercial equipment, e.g. reactors, tubes or engines

Definitions

• the invention relates to a method for cleaning objects in a pressure vessel with liquefied gases.
• DE-42 30 485 discloses a cleaning device for smaller workpieces using liquefied gases, a drum being rotatably and / or pivotably arranged in a pressure-resistant container and being connected to a drive device. By rotating the drum, both the cleaning fluid in the pressure-resistant container and the objects in the drum are set in turbulent motion, which increases the cleaning effect. Chemical solvents, mechanical abrasives and inflowing inert gases can also increase cleaning success.
• at least one lock is provided on the pressure-resistant container for loading and unloading the objects. These locks make a complete ventilation of the pressure-resistant container for the removal of the objects or for loading unnecessary.
• Liquid carbon dioxide at temperatures between 20 and approximately 30 ° C. with pressures corresponding to the vapor pressure values is used for the processes of the two steps mentioned.
• WO 94/01613 a method for cleaning textiles using liquefied or supercritical carbon dioxide is known, which is introduced at temperatures between 20 and 100 ° C. and corresponding pressures between 60 and 350 bar into a pressure vessel loaded with the textiles. After the textiles have been washed, there is a displacement flushing with a second fluid, again a compressed gas, such as air or nitrogen.
• a compressed gas such as air or nitrogen.
• WO 90/06189 a method for removing impurities from a substrate is known in that the substrate is brought into contact by means of a compressed gas with liquid-like density at critical or supercritical pressure, the phase of the gas between liquid state and supercritical state being varied the temperature of the gas is shifted in a number of stages between supercritical and subcritical temperatures.
• This multi-stage temperature variation is based on a change in the cohesive energy content of the gas dense phase.
• the aim is to make the solubility of the compressed gas effective with regard to contamination. Mechanical interactions between the compressed gas and the contaminants are not taken into account.
• the object of the present invention is therefore to develop a cleaning process with liquefied gases in which the same cleaning results can be achieved with less effort.
• This object is achieved in that the gas liquefied under pressure is introduced into the pressure vessel which contains the objects to be cleaned, that subsequently or previously the temperature of the liquefied gas is lowered below the critical temperature of the gas and that the cleaning at least is carried out essentially below the critical temperature and below the critical pressure of the gas.
• the increased mechanical interaction is due to a higher mass transport of fluid to the surface to be cleaned due to the increased density and the greater shear forces between the fluid and the substrate surface due to the increased viscosity of the fluid.
• the viscosity increases exponentially with the reciprocal of the temperature.
• noble gases such as helium or argon
• hydrocarbons such as methane, ethane, propane, ethene or propene, as well as trifluoromethane, carbon dioxide, nitrous oxide and sulfur hexafluoride are suitable as fluids.
• the liquefied gas is poured into the pressure vessel until it fills part of the same.
• the liquefied gas is then in equilibrium with its gaseous phase.
• the pressure vessel can be filled with liquefied gas until it is only in the liquid phase. Then the density and viscosity of the liquid can be increased even further if the pressure in the pressure vessel is increased while the temperature is kept constant.
• carbon dioxide is particularly preferable, being liquid and gaseous at pressures of below 60 bar Phase with temperatures between -20 and + 20 ° C is used for the cleaning process according to the invention.
• the pressure vessel can be completely filled with liquid carbon dioxide, the temperature then being kept constant at a value between -20 and + 20 ° C. and the pressure being increased to a value above the corresponding value on the vapor pressure curve .
• the mechanical interactions can be increased if the liquefied gas and / or the objects to be cleaned are circulated in the pressure vessel. This is done in a known manner by means of an impeller or a rotatable drum in the pressure vessel.
• the pressure vessel is only partially filled with liquefied gas, there is an additional frictional effect on the surface of the soiled objects when the objects to be cleaned are circulated by constant immersion and immersion out of or into the liquid phase.
• the mechanical interaction can be increased if it is operated intermittently and / or with an alternating direction of rotation.
• the method according to the invention has proven to be effective in many tests, in particular for cleaning textiles. It is also suitable to clean metal surfaces or electronic assemblies such as circuit boards from contaminants, which mostly contain organic residues.
• contaminated test tissues soiled with various fats are cleaned in a pressure vessel into which liquefied carbon dioxide is introduced.
• the pressure vessel contains a drum that rotates in the pressure vessel, whereby the textiles and the liquefied gas are moved relative to one another.
• the gas is removed from a storage container in which carbon dioxide liquefied under pressure is present at ambient temperature, and the pressure container is partially filled.
• the temperature in the pressure vessel is then reduced to approx. 10 ° C while the drum is rotated.
• the pressure container can be completely filled after a certain cleaning time, the temperature of the liquid carbon dioxide then being kept constant at about 10 ° C. while the pressure is increased to over 45 bar.
• the pressure can be increased, for example, up to 70 bar (below critical pressure).
• the cleaning results are completely sufficient even at low pressure increases, so that operating and system costs can be significantly reduced compared to previous cleaning methods.
• the procedure and a possible addition of surfactants will be selected. After cleaning, the contaminated carbon dioxide is removed and can be reused after relaxation, during which the contaminants fail. This contributes to environmental protection and further reduces costs.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Textile Engineering (AREA)
• Cleaning By Liquid Or Steam (AREA)
• Cleaning In General (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Gas Separation By Absorption (AREA)
• Treating Waste Gases (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=7756865

Family Applications (1)

Country Status (4)

Cited By (4)

Families Citing this family (38)

Citations (7)

Family Cites Families (1)

• 1995
  • 1995-03-16 DE DE19509573A patent/DE19509573C2/de not_active Expired - Fee Related
• 1996
  • 1996-03-12 AT AT96103894T patent/ATE181261T1/de not_active IP Right Cessation
  • 1996-03-12 DE DE59602213T patent/DE59602213D1/de not_active Expired - Fee Related
  • 1996-03-12 EP EP96103894A patent/EP0732154B1/fr not_active Expired - Lifetime
  • 1996-03-15 US US08/616,751 patent/US5759209A/en not_active Ceased
• 2000
  • 2000-06-02 US US09/585,581 patent/USRE38001E1/en not_active Expired - Lifetime

Patent Citations (8)

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