US3921917A - Method of comminuting of materials at low temperatures - Google Patents

Method of comminuting of materials at low temperatures Download PDF

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Publication number
US3921917A
US3921917A US449840A US44984074A US3921917A US 3921917 A US3921917 A US 3921917A US 449840 A US449840 A US 449840A US 44984074 A US44984074 A US 44984074A US 3921917 A US3921917 A US 3921917A
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United States
Prior art keywords
gas
gas stream
materials
cold
cooling
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US449840A
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English (en)
Inventor
Helmut Meinass
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Linde GmbH
Original Assignee
Linde GmbH
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Filing date
Publication date
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Publication of US3921917A publication Critical patent/US3921917A/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C19/00—Other disintegrating devices or methods
    • B02C19/18—Use of auxiliary physical effects, e.g. ultrasonic waves or irradiation, for disintegrating
    • B02C19/186—Use of cold or heat for disintegrating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B29B17/04—Disintegrating plastics, e.g. by milling
    • B29B17/0404—Disintegrating plastics, e.g. by milling to powder
    • B29B17/0408—Disintegrating plastics, e.g. by milling to powder using cryogenic systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2007/00—Flat articles, e.g. films or sheets
    • B29L2007/008—Wide strips, e.g. films, webs
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S241/00—Solid material comminution or disintegration
    • Y10S241/37—Cryogenic cooling

Definitions

  • the present invention relates to a method of comminuting materials frangible at low temperatures and, more particularly, to a system for the comminution of synthetic-resin foil scraps and the like which are embrittled at cryogenic temperatures and are milled at such temperatures.
  • regrind i.e. comminuted synthetic resins which are transformed from foil or sheet scrap into a powder for reuse in extrusion or other forming processes.
  • the cooling-gas stream is brought into contact with the material to be milled while a carrier gas entrains the material into the mill and is conducted therefrom.
  • the nitrogen is thus branched into a cooling-gas stream and a carrier-gas stream withthe cooling-gas stream traversing the material to be milled in a cooling column while the carrier-gas stream subsequently entrains the material into the mill.
  • a portion of the cooling gas after heating in the cooling column can be passed with a portion of the carrier gas separated from the product to a blower which generates the kinetic energy of the gas streams required to displace them and entrain the material to be comminuted, while liquefied gas is expanded into the gas to cool the latter.
  • the injection of expanding liquid into the gas stream prior to its subdivision into the cooling gas portion and the carrier gas portion serves to abstract heat which has been picked up from the product to be chilled prior to and during milling.
  • thermoplastic synthetic-resin foils From the point of view of energy economy, the process has a disadvantage.
  • thermoplastic synthetic-resin foils it is generally necessary to provide extremely low temperatures and hence relatively large volumes of cooling gas and thus to utilize large amounts of energy to generate the correspondingly large amounts of cooling gas which are necessary.
  • Another object of this invention is to provide an improved method for the low-temperature milling of materials such as thermoplastic synthetic-resin foil straps.
  • the present improvement is based upon by discovery that the use of a subatmospheric pressure at critical points in the system can provide a significant reduction in the energy consumption and gas throughput of a system for the low-temperature milling of materials of the type described.
  • the pressure reduction has the further advantage that it permits 'theincrease of gas density with lowering temperature, which has hitherto caused significant difficulties in earlier systems, to be substantially completely eliminated.
  • the problems arising from such increasing gas density in the region of the active tools of the mill are thereby eliminated and a more effective. comminution is obtained since the kinetic energy of the material to be comminuted is less readily absorbed by the surrounding gas.
  • the improvement is mostpronounced, of course, in impact, pin and attrition mills.
  • the subatmospheric pressure is preferably generated by ejecting a portion of the gasesinto the atmosphere through a compressor so that the system sustains a subatmospheric pressure at the compressor or suction pump of 0.1 to 0.4 bar, preferably 0.2 bar.
  • a saving is empirically found in the proportionality between energy loss by friction and pressure. taking into consideration the cold losses of friction (see the foregoing table) of 8071 (cold loss by friction) of 16% (proportionality factor between energy and pressure) of 1/5 (ratio of absolute pressure '-O.Z bar of present method to absolute pressure l barof conventional system).
  • the milled product is passed in counterflow to the cold gas stream traversing the system so that a portion of the "cold carried by the milled product is taken up by the cooling gas and is eventually utilized in the system. This reduces losses of cold from the system and increases the thermal efficiency thereof.
  • a loss of cold is equivalent to absorption of heat and vice versa.
  • a gain of cold is equivalent to an abstraction of heat and vice versa. and it is only for convenience that gain and loss of cold are used in place of the loss and gain of heat, respectively.
  • the transfer of cold from the milled product and the warming thereof in heat exchange with the cooling gas to be used elsewhere in the system has the additional advantage that condensation upon the milled product because of moisture in the atmosphere when the milled product is at a temperature below the dewpoint of the atmosphere is avoided.
  • the heat transfer from the. milled product is best carried out according to the invention by passing the milled product through a cascade of cyclones and recovering from the cyclones. gas which is cooled by in-. jection ofliquefied gas and mixed with the cooling and-,
  • the blocking gas can be provided at the inlet for the material to be milled and at the outlet for the milled product.
  • the cold blocking gas can be drawn from the gas phase or space of a storage vessel for liquefied gas.
  • Apparatus for carrying out theprocess of the present invention comprises a mill at the discharge end of a cooling column or tower which is provided with an injector mixer via a filter as well as with a duct system1 having at least two compressors.
  • FIGURE of the drawing is a flow diagram of a system embodying the present in:
  • the apparatus of the present invention comprises a hopper 1 whose funnel shaped bottom is provided'with i i a cell-wheel gate 2 opening into an intermediate receptacle 3 having a funnel shaped bottom communicating 1:
  • the cooling gas is introduced to the perforated frustoconical bottom of this column 5 through a valve 9 and the cold solids pass through another rotary-cell medevice tering device 6 into an impact pin or attrition mill 7.
  • the pin mill 7 has an axial inlet and a peripheraloutlet I as described and illustrated at pages 8 38to 8 Q 40'of PERRYS CHEMICAL ENGINEERS HANDBOOK,
  • the product outlet of the mill. which is driven by an. electric motor. communicates with the first cycloneof a cascade l0, l4, l5 and 16 of cyclones, eachiof which 1 is separated from the next cyclone by a rotary gate 1'1,
  • a storage vessel for liquefied gas is represented at 41 and the li.q-, I
  • uefied gas may be injected via line 21 and a venturitype mixer 22 into the system at the inlet ofacompres- I i sor 23.
  • the other compressor of the system is shown at 1 26 and various ducts are provided at 29-37 to supply I cold gas from a line 24 and the gas phase above the storage vessel 41 to the variousvalves, bearings and seals which are not hermetic. to serve as a blocking gas for release into theatmosphere or to prevent induction of moisture'laden air from the atmosphere.
  • the product to bemilled e.g. thermo- 1 plastic scrap foil as described in the aforementioned patent. is fed from the hopper or storage receptacle 1 through the solids-metering gate 2 into an intermediate.
  • the compressor 26 thus maintains a subatmosphericpressure of said 0.2 bar in the system. i t
  • cyclone l0 and cyclone 14 it is passed through a filler 20 and returned through the venturi mixer 22 to the inlet of the compressor 23.
  • the gas By admixture with expanding liquefied gas supplied at line 21, the gas is recooled and delivered at 9 to the cooling tower.
  • a portion of the gas stream displaced by the compressor 23 is branched via valve 8 to serve as a carrier gas entraining the cold material to be milled from the gate 6 through the mill 7.
  • the carrier gas transverses the mill 7 with the cold material which is subdivided in the mill to a powder.
  • the carrier gas and the powder enter the uppermost cyclone 10 of the cascade and the solid material passes from cyclone 10 through gate 11 to cyclone 14.
  • the carrier gas is returned to the filter 20 at the cyclone 10.
  • cyclones 14, 15 and 16 the comminuted product is subjected to treatment with the previously warmed cooling gas stream as already described.
  • the gates 2, 4, 6, 11, 12, 13, 17 and 19 may be of the rotary air-lock type illustrated and described at p. 7-33 of PERRYS CHEMICAL ENGINEERS HANDBOOK, op. cit.
  • Compressor 26 is so dimensioned that it draws off ex actly the same volume of gas which is supplied by the tank 41. Thus, the subatmospheric pressure in the entire system remains constant, once established.
  • Compressor 23 and valves 8 and 9 are so set that the gas quantity per unit time fed by compressor 23 into the column 5 is greater than that removed from column 5 by compressor 26. Thus, the difference is passed by line 27 to the cyclone l6 and is circulated. The circulation of gases through the system is thus effected by compressor 23.
  • compressor 23 passes a first portion of a carrier gas stream via valve 8 through the mill 7 along a closed path through the heat exchanger and unit 22 back to the compressor 23.
  • a first portion of the cold gas stream is circulated along a closed path through the valve 9 to the cooling 6 column 5 via line 27 to the cyclones 16, 15 and 14 in succession before being returned to the heat exchanger 20, unit 22 and the compressor 23.
  • a second portion of the latter gas stream is discharged via line 25 into the atmosphere through the compressor 26 and the first portion of the two gas streams are fed into one another just ahead of the heat exchanger 20.
  • the cold gas stream emerging from the cascaded cyclones l6, l5, 14 is further cooled by the injections of liquefied gas at 22.

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  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Food Science & Technology (AREA)
  • Disintegrating Or Milling (AREA)
  • Crushing And Grinding (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
US449840A 1973-03-09 1974-03-11 Method of comminuting of materials at low temperatures Expired - Lifetime US3921917A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2311933A DE2311933C3 (de) 1973-03-09 1973-03-09 Verfahren und Vorrichtung zur Zerkleinerung von Stoffen bei tiefen Temperaturen

Publications (1)

Publication Number Publication Date
US3921917A true US3921917A (en) 1975-11-25

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US449840A Expired - Lifetime US3921917A (en) 1973-03-09 1974-03-11 Method of comminuting of materials at low temperatures

Country Status (11)

Country Link
US (1) US3921917A (de)
AT (1) AT327658B (de)
BE (1) BE812095A (de)
BR (1) BR7401798D0 (de)
CH (1) CH570202A5 (de)
DE (1) DE2311933C3 (de)
ES (1) ES424119A1 (de)
FR (1) FR2220309B3 (de)
NL (1) NL7316936A (de)
NO (1) NO740817L (de)
ZA (1) ZA741563B (de)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3985086A (en) * 1975-06-09 1976-10-12 The Raymond Lee Organization, Inc. Freezer, vacuum, oven sewage treatment system
US4090669A (en) * 1976-05-28 1978-05-23 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process for embrittling integuments of small seeds
US4102503A (en) * 1975-04-16 1978-07-25 Linde Aktiengesellschaft Method of and apparatus for the low-temperature milling of materials
US4222527A (en) * 1979-02-22 1980-09-16 Union Carbide Corporation Cryopulverizing packed bed control system
US4269693A (en) * 1978-05-30 1981-05-26 Hastie Anthony M B Process for recovering bitumen from waste bituminous products
US4511091A (en) * 1983-01-06 1985-04-16 Augusto Vasco Method and apparatus for recycling thermoplastic scrap
US4645131A (en) * 1984-12-24 1987-02-24 Hailey Robert W Powder milling method to produce fine powder sizes
US4692982A (en) * 1986-05-22 1987-09-15 Rice Norman B Lining removal process
US4846408A (en) * 1988-01-21 1989-07-11 Gentex Corporation Method for making a friction material
US5301881A (en) * 1991-12-02 1994-04-12 Hitachi, Ltd. System for disposing waste
US5533680A (en) * 1994-12-28 1996-07-09 U.S. Rubber Reclaiming, Inc. Process to grind thermoset or thermoplastic materials
US5887803A (en) * 1995-09-07 1999-03-30 Messer Griesheim Gmbh Process and apparatus for grinding and sifting a product
US6076752A (en) * 1998-06-01 2000-06-20 Quality Botanical Ingredients, Inc. Method and apparatus for inert gas purging/temperature control for pulverizing/grinding system
US20040231342A1 (en) * 2001-11-15 2004-11-25 Soon-Jin Hong Freeze-grinding method of the waste materials using the cooled air
WO2016029892A1 (de) * 2014-08-26 2016-03-03 Netzsch Trockenmahltechnik Gmbh Verfahren zur klassierung von feststoff-produktfraktionen, trennvorrichtung und zerkleinerungsanlage
US20170043351A1 (en) * 2015-08-13 2017-02-16 Lehigh Technologies, Inc. Systems, methods, and apparatuses for manufacturing micronized powder

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5597123A (en) * 1995-06-30 1997-01-28 Praxair Technology, Inc. Ultra-high energy cryogenic impact system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2609150A (en) * 1949-11-05 1952-09-02 Union Carbide & Carbon Corp Mechanical pulverization of refrigerated plastics
US3460769A (en) * 1965-07-20 1969-08-12 Herbert Alfred Merges Method and apparatus for reclaiming rubber scrap
US3633830A (en) * 1968-05-10 1972-01-11 Linde Ag Process and apparatus for the comminution of soft material
US3818976A (en) * 1969-12-01 1974-06-25 Inventa Ag Process and apparatus for grinding granular materials at low temperatures

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2609150A (en) * 1949-11-05 1952-09-02 Union Carbide & Carbon Corp Mechanical pulverization of refrigerated plastics
US3460769A (en) * 1965-07-20 1969-08-12 Herbert Alfred Merges Method and apparatus for reclaiming rubber scrap
US3633830A (en) * 1968-05-10 1972-01-11 Linde Ag Process and apparatus for the comminution of soft material
US3818976A (en) * 1969-12-01 1974-06-25 Inventa Ag Process and apparatus for grinding granular materials at low temperatures

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4102503A (en) * 1975-04-16 1978-07-25 Linde Aktiengesellschaft Method of and apparatus for the low-temperature milling of materials
US3985086A (en) * 1975-06-09 1976-10-12 The Raymond Lee Organization, Inc. Freezer, vacuum, oven sewage treatment system
US4090669A (en) * 1976-05-28 1978-05-23 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process for embrittling integuments of small seeds
US4269693A (en) * 1978-05-30 1981-05-26 Hastie Anthony M B Process for recovering bitumen from waste bituminous products
US4222527A (en) * 1979-02-22 1980-09-16 Union Carbide Corporation Cryopulverizing packed bed control system
US4511091A (en) * 1983-01-06 1985-04-16 Augusto Vasco Method and apparatus for recycling thermoplastic scrap
US4645131A (en) * 1984-12-24 1987-02-24 Hailey Robert W Powder milling method to produce fine powder sizes
US4692982A (en) * 1986-05-22 1987-09-15 Rice Norman B Lining removal process
US4846408A (en) * 1988-01-21 1989-07-11 Gentex Corporation Method for making a friction material
US5301881A (en) * 1991-12-02 1994-04-12 Hitachi, Ltd. System for disposing waste
US5533680A (en) * 1994-12-28 1996-07-09 U.S. Rubber Reclaiming, Inc. Process to grind thermoset or thermoplastic materials
US5887803A (en) * 1995-09-07 1999-03-30 Messer Griesheim Gmbh Process and apparatus for grinding and sifting a product
US6076752A (en) * 1998-06-01 2000-06-20 Quality Botanical Ingredients, Inc. Method and apparatus for inert gas purging/temperature control for pulverizing/grinding system
US20040231342A1 (en) * 2001-11-15 2004-11-25 Soon-Jin Hong Freeze-grinding method of the waste materials using the cooled air
US6923392B2 (en) * 2001-11-15 2005-08-02 Kolon Construction Co., Ltd. Freeze-grinding method of the waste materials using the cooled air
WO2016029892A1 (de) * 2014-08-26 2016-03-03 Netzsch Trockenmahltechnik Gmbh Verfahren zur klassierung von feststoff-produktfraktionen, trennvorrichtung und zerkleinerungsanlage
US20170043351A1 (en) * 2015-08-13 2017-02-16 Lehigh Technologies, Inc. Systems, methods, and apparatuses for manufacturing micronized powder
EP3130404A3 (de) * 2015-08-13 2017-05-03 Lehigh Technologies, Inc. Verfahren zur herstellung von mikronisiertem pulver
EP3470197A1 (de) * 2015-08-13 2019-04-17 Lehigh Technologies, Inc. Verfahren zum tiefkaltem schleifen von partikeln
US10675634B2 (en) * 2015-08-13 2020-06-09 Lehigh Technologies, Inc. Systems, methods, and apparatuses for manufacturing micronized powder

Also Published As

Publication number Publication date
NL7316936A (de) 1974-09-11
ES424119A1 (es) 1976-06-16
FR2220309B3 (de) 1977-07-15
CH570202A5 (de) 1975-12-15
NO135969B (de) 1977-03-28
FR2220309A1 (de) 1974-10-04
DE2311933A1 (de) 1974-09-19
BR7401798D0 (pt) 1974-11-19
ZA741563B (en) 1975-02-26
AT327658B (de) 1976-02-10
ATA166574A (de) 1975-04-15
NO135969C (de) 1977-07-06
NO740817L (no) 1974-09-10
DE2311933C3 (de) 1979-12-20
BE812095A (fr) 1974-07-01
DE2311933B2 (de) 1979-04-26

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