US3818976A - Process and apparatus for grinding granular materials at low temperatures - Google Patents

Process and apparatus for grinding granular materials at low temperatures Download PDF

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Publication number
US3818976A
US3818976A US00093824A US9382470A US3818976A US 3818976 A US3818976 A US 3818976A US 00093824 A US00093824 A US 00093824A US 9382470 A US9382470 A US 9382470A US 3818976 A US3818976 A US 3818976A
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US
United States
Prior art keywords
gas
heat exchanger
heat
grinding
temperature
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
US00093824A
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English (en)
Inventor
A Ledergerber
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Inventa AG fuer Forschung und Patentverwertung
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Inventa AG fuer Forschung und Patentverwertung
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to CH1788569A priority Critical patent/CH491675A/de
Application filed by Inventa AG fuer Forschung und Patentverwertung filed Critical Inventa AG fuer Forschung und Patentverwertung
Priority to US00093824A priority patent/US3818976A/en
Application granted granted Critical
Publication of US3818976A publication Critical patent/US3818976A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • B29B13/00—Conditioning or physical treatment of the material to be shaped
    • B29B13/10—Conditioning or physical treatment of the material to be shaped by grinding, e.g. by triturating; by sieving; by filtering
    • 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
    • B29B13/00—Conditioning or physical treatment of the material to be shaped
    • B29B13/02—Conditioning or physical treatment of the material to be shaped by heating
    • B29B13/021—Heat treatment of powders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/004—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being air
    • 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

  • pre-ground solid car-' bon dioxide may be admixed with a pre-cooled charging product before it enters the grinding mill.
  • the heat of grinding is then removed by a cooling medium, both partly from the pre-cooled charging product and from the vaporizing residual dry ice (solid CO)
  • solid CO vaporizing residual dry ice
  • Another possibility consists in the use of liquid nitrogen as a cooling medium. If there is direct contact between the liquid nitrogen and the charging product, the extremely low temperature may produce an impairment of the comminution properties of the charging product.
  • the heat generated during grinding is removed from the mill by a cooled gas circuit which for its part gives up the absorbed heat via a first heat exchanger to a cold-gas circuit, the necessary refrigerating capacity being produced by an approximately isentropic expansion of a compressed gas in one or more expansion machines.
  • the expanded gas after absorbing the heat in the first heat exchanger, is heated in a second heat exchanger to approximately ambient temperature by transfer of heat to the same gas compressed in an interposed compressor, which is cooled to the intake temperature of the expansion machines in counter-current to the heat-absorbing gas stream.
  • cold gas turbines as customarily used in gas liquefying plants may be employed as expansion machines.
  • the braking of the turbines may either be effected electrically with the interposition of a conventional gearing mechanism,
  • turbocompressors and reciprocating compressors may be employed for gas compression, depending upon the size of the required refrigerating capacity and on the pressure ratio employed.
  • Air is preferably employed as recycle gas, since in this way the cost of topping up the system in the event of leakage losses is low.
  • gases which are not liquefied in the working range may also be employed.
  • the process according to the invention allows the temperature during the grinding operation to be adjusted simply and within wide limits to any desired level and to be kept exactly constant thereat. Regulation may be effected by varying the pressure gradient in the refrigerating circuit, by varying the amount of gas in circulation or by varying the effective heat-exchanger area.
  • the cost of cold production by the new process is substantially smaller than in the case of the other processes that are known and operation is extremely simple in comparison to known processes.
  • the heat of compression is given off and the air finally passes through the pipe 27 back to the heat exchanger 3, in which the re-cycled air is cooled to the turbine intake temperature of -60 C.
  • the stream of air contained in pipe 34 is cooled to l00 C in the heat exchanger 2 and recycled to pipe 30 to a fluidized bed cooler 11, in which the plastics granules fed from the supply vessel 10 are pre-cooled.
  • the mixture of air and granules passes through the pipe 31 to the mill 12, in which the granules are crushed into powder.
  • the heat of grinding that is generated is removed from the stream of charging product, as a result of which the air temperature increases to 60 C.
  • the powder is separated from the recycled air in the separator l3 and is conveyed to a screening arrangement through valve 37, while the air is carried back to the heat exchanger 2 by the fan 14.
  • Conduit 35 (dotted lines) may be used in an alternative embodiment to recycle a portion of the heated air to pipe 30 to somewhat raise and regulate the temperature of air in conduit 30.
  • Appropriate conventional valves may be used to achieve this.
  • the first is indicated generally by numeral 40 and carclosed gas circuit indicated generally by numeral 42 and is the circuit used to control the temperature of the gas flowing in the first circuit 40.
  • the only element common to both circuits is heat exchanger 2, although the gases contained in the two circuits are not intermixed with each other by heat exchanger 2.
  • a process for controlling the temperature of granular material during grinding in a grinding mill of the type in which the granular material is mixed with a cold gas prior to grinding, separated from the ground material after grinding, recooled in a heat exchanger and then reused to cool additional granular material during grinding comprising the steps of feeding a gas which is cooler than the separated gas to the first heat exchanger such that the separated gas gives up at least a portion of its heat to said cooler gas, then heating said gas to approximately ambient temperature in a second heat exchanger, expanding said heated gas substantially isentropically to a predetermined cooler temperature in an expansion machine and recycling said cooler gas to said first heat exchanger.
  • step of heating the gas in the second heat exchanger comprises the steps of feeding gas having a temperature greater than that of the gas to be heated into the second heat exchanger, the warmer gas being fed into said second heat exchangerin counter-current to the direction of flow of the gas to be warmed.
  • Process for grinding granular materials, in particular granular plastics, at low temperatures characterized in that the heat generated during grinding is removed from the mill by a cooled gas circuit which for its part gives up the absorbed heat via a first heat exchanger to a cold-gas circuit, the necessary refrigerating capacity being produced by an approximately isentropic expansion of a compressed gas in one or more expansion machines, and the expanded gas, after the heat absorption effected in the first heat exchanger, being heated in a second heat exchanger to approxi mately ambient temperature by transfer of heat to the same gas compressed in an interposed compressor, which is cooled to the intake temperature of the expansion machines in counter-current to the heat-absorbing gas stream.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Food Science & Technology (AREA)
  • Disintegrating Or Milling (AREA)
US00093824A 1969-12-01 1970-11-30 Process and apparatus for grinding granular materials at low temperatures Expired - Lifetime US3818976A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CH1788569A CH491675A (de) 1969-12-01 1969-12-01 Verfahren zum mahlen von körnigen materialien bei tiefen temperaturen
US00093824A US3818976A (en) 1969-12-01 1970-11-30 Process and apparatus for grinding granular materials at low temperatures

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH1788569A CH491675A (de) 1969-12-01 1969-12-01 Verfahren zum mahlen von körnigen materialien bei tiefen temperaturen
US00093824A US3818976A (en) 1969-12-01 1970-11-30 Process and apparatus for grinding granular materials at low temperatures

Publications (1)

Publication Number Publication Date
US3818976A true US3818976A (en) 1974-06-25

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Application Number Title Priority Date Filing Date
US00093824A Expired - Lifetime US3818976A (en) 1969-12-01 1970-11-30 Process and apparatus for grinding granular materials at low temperatures

Country Status (2)

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US (1) US3818976A (de)
CH (1) CH491675A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3921917A (en) * 1973-03-09 1975-11-25 Linde Ag Method of comminuting of materials at low temperatures
US4056231A (en) * 1975-08-07 1977-11-01 British Steel Corporation Scrap treatment
US4102503A (en) * 1975-04-16 1978-07-25 Linde Aktiengesellschaft Method of and apparatus for the low-temperature milling of materials
US4846408A (en) * 1988-01-21 1989-07-11 Gentex Corporation Method for making a friction material
JP3390801B2 (ja) 1995-03-16 2003-03-31 日本酸素株式会社 低温破砕装置における被破砕物の冷却方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2153416C1 (ru) * 1999-01-12 2000-07-27 Колесников Игорь Владимирович Установка для криогенного измельчения пластмасс

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2400382A (en) * 1943-07-29 1946-05-14 Gerald D Arnold Closed hammer mill circuits

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2400382A (en) * 1943-07-29 1946-05-14 Gerald D Arnold Closed hammer mill circuits

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3921917A (en) * 1973-03-09 1975-11-25 Linde Ag Method of comminuting of materials at low temperatures
US4102503A (en) * 1975-04-16 1978-07-25 Linde Aktiengesellschaft Method of and apparatus for the low-temperature milling of materials
US4056231A (en) * 1975-08-07 1977-11-01 British Steel Corporation Scrap treatment
US4846408A (en) * 1988-01-21 1989-07-11 Gentex Corporation Method for making a friction material
JP3390801B2 (ja) 1995-03-16 2003-03-31 日本酸素株式会社 低温破砕装置における被破砕物の冷却方法

Also Published As

Publication number Publication date
CH491675A (de) 1970-06-15

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