Process and apparatus for the comminution of soft material

Claim 2

The process defined in claim 2 wherein said portion of said stream is cooled by injecting into same a spray of liquefied gas, vapors of said liquefied gas being thereafter entrained as part of said chilling-gas stream.

Claim 3

The process defined in claim 2 wherein said portion of said stream is cooled by passing it in indirect heat exchange with a bath of said liquefied gas, thereby transferring sensible heat to said bath.

Claim 4

The process defined in claim 4, further comprising the step of vaporizing a portion of the liquefied gas with the heat transferred to said bath and combining the vapors of the liquefied gas thus resulting with the stream recirculated into contact with said pieces.

Claim 5

The process defined in claim 2, further comprising the step of drying said pieces of soft material with a portion of said chilling-gas stream after warming of said portion by absorption of heat from the pieces of said material contacted thereby.

Claim 6

A process for the comminution of pieces of relatively soft material, comprising the steps of: passing the pieces of said soft material countercurrent to a chilling-gas stream and into direct contact therewith to rigidify said pieces; recirculating at least part of said stream after its contact with said material into contact with further quantities of the material; thereafter milling the rigidified pieces prior to substantial warming thereof; and entraining the rigidified pieces to the milling step and carrying the milled product from the zone in which it Is milled in a recirculating transport-gas stream.

Claim 7

The process defined in claim 7, further comprising the step of filtering said recirculating transport-gas stream prior to its return to said milling stage.

Claim 8

The process defined in claim 8 wherein said pieces are milled with a rotary member, said process further comprising the step of sealing said member against the escape of particles to the atmosphere with at least a portion of the recirculated filtered transport-gas stream.

Claim 9

The process defined in claim 7, further comprising the step of maintaining the temperature of said transport-gas stream substantially constant at least at entry of said transport-gas stream to the milling zone.

Claim 10

The process defined in claim 7, further comprising the step of cooling said transport gas stream by diverting a portion of said transport gas stream from the recirculating path, combining said portion with said chilling-gas stream and drawing part of the chilling-gas stream into said transport -gas stream.

Claim 11

An installation for the comminution of pieces of relatively soft material, comprising: means forming a chilling chamber adapted to receive pieces of soft material for displacement therein in one direction; circulating means for recirculating a chilling-gas stream through said chamber countercurrent to the movement of said pieces therethrough and in direct heat exchange with said pieces, thereby cooling said pieces and rigidifying same; and milling means connected to said chamber for connecting the rigidified pieces prior to substantial warming thereof; said means forming said chilling chamber being an upright column having a drying chamber at an upper portion thereof and said chilling chamber below said drying chamber, said pieces passing downwardly through said chambers in succession, said drying chamber having a larger cross section than said chilling chamber, said circulating means including outlet means at the bottom portion of said chilling chamber and drawing partially warm chilling gas from said chilling chamber, respectively.

Claim 12

An installation as defined in claim 12, further comprising precomminuting means at the bottom of said chilling chamber for reducing the size of the rigidified pieces prior to the passage thereof to said milling means, and a duct connecting the bottom of said chilling chamber with said milling means for conveying precomminuted pieces of the rigidified material thereto.

Claim 13

An installation as defined in claim 12 wherein said outlet means includes a perforated pipe opening upwardly and centrally into said chilling chamber below said precomminuting means.

Claim 14

An installation as defined in claim 12 wherein said circulating means includes blower means interconnecting said inlet means and said outlet means for displacing said chilling-gas stream along a closed path, and filter means between said blower means and said inlet means for removing particles entrained with said partially warmed chilling gas.

Claim 15

An installation as defined in claim 15, further comprising means along said path for cooling at least part of the recirculated chilling-gas stream prior to its return to said outlet means in heat-exchange with a liquefied gas.

Claim 16

An installation as defined in claim 16 wherein the means for cooling said part of said recirculated chilling-gas stream includes means for injecting liquefied gas into said stream.

Claim 17

An installation as defined in claim 16 wherein the means for cooling said part of said chilling-gas stream includes a bath of liquefied gas, and a heat-exchange loop extending into said bath for passing said part of said chilling-gas stream through said loop into heat exchange with the liquefied gas of said bath to transfer sensible heat to said bath.

Claim 18

An installation as defined in claim 18 wherein said sensible heat transfer to said bath vaporizes a portion of said liquefied gas, further comprising means for combining the vapors of said liquefied gas with said part of the chilling-gas strEam passed through said loop.

Claim 19

An installation as defined in claim 16, further comprising means for controlling the temperature of the chilling-gas stream admitted to said chilling chamber and including means for selectively establishing the proportion of the recirculated chilling-gas stream subjected to cooling with said liquefied gas.

Claim 20

An installation for the comminution of pieces of relatively soft material, comprising: means forming a chilling chamber adapted to receive pieces of soft material for displacement therein in one direction; circulating means for recirculating a chilling-gas stream through said chamber countercurrent to the movement of said pieces therethrough and in direct heat exchange with said pieces, thereby cooling said pieces and rigidifying same; milling means connected to said chamber for connecting the rigidified pieces prior to substantial warming thereof; and means for recirculating a transport-gas stream through said milling means for conveying rigidified pieces of said material to said milling means and carrying the milled product away from said milling means, said milling means including a pinned-disk mill connected with said chilling chamber, and a collecting receptacle connected with said mill for accumulating the milled product, said means for recirculating said transport-gas stream including means forming a closed circulating path provided with a blower and a filter upstream of said blower for removing particles entrained with the transport gas prior to the passage of the transport gas through said blower.

Claim 21

An installation as defined in claim 21, further comprising temperature-control means in said filter for maintaining the temperature of said transport-gas stream substantially constant at least upon entry of the transport gas into said mill.

Claim 22

An installation as defined in claim 22 wherein said temperature-control means includes refrigerator means in said filter.

Claim 23

An installation as defined in claim 21 wherein said mill has a housing for at least one rotary member journaled in said housing, said blower being constructed and arranged to introduce said transport gas between said rotary member and said housing at a pressure and velocity sufficient to prevent escape of dust from said mill to the atmosphere.

Claim 24

An installation as defined in claim 21 further comprising conduit means connecting said path with the circulating means for recirculating said chilling-gas stream to permit transfer of gas between said streams.

Claim 25

An installation as defined in claim 25 wherein said conduit means includes a duct connected with said filter and a valve in said duct controlling the transfer of gas between said streams.

Claim 26

An installation as defined in claim 21, further comprising a duct connecting said chilling chamber with said mill, and means including a valve connecting the circulating path of said transport gas stream with said duct.

Claim 27

A process for the comminution of pieces of relatively soft material, comprising the steps of: a. passing the pieces of said soft material in direct contact with and countercurrent to a circulating chilling-gas stream to rigidify said pieces; b. branching off at least part of this circulating chilling-gas stream after a substantial warming thereof from abstraction of heat from said pieces; c. cooling the branched portion of said chilling-gas stream and returning the cooled portion to said circulating chilling-gas stream for contact with additional pieces of said soft material in accordance with step (a); and d. milling the rigidified pieces prior to substantial warming thereof.