Refrigeration – Cryogenic treatment of gas or gas mixture – Solidification
Reexamination Certificate
1999-06-17
2001-02-20
Doerrler, William (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Solidification
C062S605000
Reexamination Certificate
active
06189336
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates broadly to apparatus for manufacturing solid carbon dioxide particles, known to those skilled in the art as carbon dioxide snow. More specifically, the present invention relates to a method and apparatus for facilitating the formation, capture and compression of snow-like carbon dioxide particles into structures that are ready for packaging, use or future processing.
Solid carbon dioxide, or dry ice, has long been used for a variety of desirable cooling purposes. Previous methods of converting liquid carbon dioxide to a solid were slow and required the use of expensive manufacturing equipment.
In one manufacturing method described in Rupp, U.S. Pat. No. 2,570,074, purified carbon dioxide is first passed through a condensing zone to convert the vaporous material to its liquid state. Next, a vent zone receives the liquid carbon dioxide and removes any uncondensed gases. The remaining liquid carbon dioxide is then passed through a reducing valve and flashed into a zone maintained at a uniform temperature and pressure. Crystals that form and settle within this zone are withdrawn from the chamber. A fine spray of water introduced into the zone flows down the sides of the chamber with carbon dioxide solidifying on the surface of the water as carbon dioxide ice. This carbon dioxide ice is then collected and passed to a hopper outside the chamber. Any vaporous carbon dioxide in the chamber may be recycled back into the system after being compressed.
In another dry ice manufacturing process, described in Rupp, U.S. Pat. No. 2,608,838, results were obtained through cooling occurring in the solidification zone by means of a circulating gas. This gas preferably boils at a lower temperature than does carbon dioxide and cooling takes place by directly cooling the carbon dioxide gas. The gas may be a vaporizing refrigerant such as methane, nitrogen, ethane or ethylene.
Love, U.S. Pat. No. 4,415,346 describes a carbon dioxide snow horn for dry ice production that utilizes a downwardly directed skirt opened at its lower, larger diameter end. The upper, smaller diameter head allows introduced liquid carbon dioxide to expand inside the skirt. A gas venting system around the skirt allows exhaust gas to be withdrawn from the chamber.
Manufacturing methods currently in use in the dry ice industry can be complex, inefficient and slow. Production rates of current machines are limited because their operating cycles include separating the solid carbon dioxide particles from a closed volume of carbon dioxide gas (typically by settling) followed by venting of the gas and, finally, compression into solid pellets or blocks. The cycle time is primarily driven by the time it takes for the particles to settle and is typically on the order of 40-50 seconds. As a result, a high capacity machine can typically provide no more than 1500-2500 pounds of dry ice per hour.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved liquid carbon dioxide conversion apparatus for converting liquid carbon dioxide to solid carbon dioxide particles and compressing them to form solid carbon dioxide structures such as pellets or blocks.
It is also an object of the present invention to provide a liquid carbon dioxide conversion apparatus that permits rapid, efficient collection and compression of particulate carbon dioxide converted from liquid carbon dioxide while capturing carbon dioxide converted to a gas during the process. The captured gaseous carbon dioxide is then available for reconversion to a liquid.
Another object of the present invention is to provide an improved method of manufacturing solid carbon dioxide articles formed from compressed particulate carbon dioxide. The method includes using a piston in a compression chamber to which is attached at least one accumulation chamber wherein the piston seals the accumulation chamber while particulate carbon dioxide is being formed and accumulated therein. When desired, the piston can be moved to allow the particulate carbon dioxide to be transferred to the compression chamber where it can be compressed into a block or extruded to form pellets.
It is a further object of the present invention to provide an apparatus for manufacturing solid carbon dioxide articles formed from compressed particulate carbon dioxide using a piston in a compression chamber to which is attached a plurality of accumulation chambers wherein the piston seals each accumulation chamber while particulate carbon dioxide is being formed and accumulated therein. The piston can then be moved to allow the particulate carbon dioxide to be transferred to the compression chamber where it can be compressed into a block or extruded to form pellets.
Another object of the present invention is to provide an improved method of converting liquid carbon dioxide to solid carbon dioxide using an apparatus that includes an accumulator housing and an inner filter defining an accumulation chamber in fluid communication with a compression chamber through a transfer portal. The method includes injecting liquid carbon dioxide into the accumulation chamber for phase transition to a mixture of gaseous and solid particulate carbon dioxide while a piston disposed within the compression chamber seals the transfer portal. The filter permits passage of the gas for collection external to the apparatus and traps the solid particles for accumulation.
To those ends, a liquid carbon dioxide conversion apparatus according to the present invention, includes a compression housing defining a compression chamber and at least one transfer portal in fluid communication with the compression chamber. The conversion apparatus further includes an assembly for converting liquid carbon dioxide to particulate solid carbon dioxide, including at least one snow accumulation chamber in fluid communication with the at least one transfer portal. Also included are means for transferring particulate solid carbon dioxide from each snow accumulation chamber to the compression chamber through a transfer portal. The conversion apparatus also includes a compression piston movably mounted in the compression chamber. The compression piston is configured for compressing particulate solid carbon dioxide accumulated within the compression chamber. The compression piston may be positioned within the compression chamber to seal the at least one transfer portal.
The compression chamber of a liquid carbon dioxide conversion apparatus according to the present invention preferably has first and second open ends. The first open end is preferably configured for receiving the compression piston into the compression chamber.
In one embodiment of the liquid carbon dioxide conversion apparatus according to the present invention, an extruder plate is removably attached to the compression housing in covering relation to the second end of the compression chamber. The extruder plate has at least one extrusion hole extending therethrough in communication with the compression chamber. Particulate solid carbon dioxide pressed against the extruder plate by the compression piston will be forced through the extrusion holes to form extruded solid carbon dioxide pellets. The compression chamber of this embodiment is preferably formed with a generally cylindrical configuration.
In another embodiment of the liquid carbon dioxide conversion apparatus according to the present invention, a movable compression wall is attached to the compression housing and is selectively movable in and out of covering relation with the second end of the compression chamber. Particulate solid carbon dioxide may be compressed by the compression piston against the compression wall when the compression wall is in covering relation with the second end of the compression chamber, thereby forming a block of solid carbon dioxide.
The assembly for transferring particulate solid carbon dioxide preferably includes a transfer piston movably mounted within each snow accumulation chamber. Particulate solid carbon dioxide within
Doerrler William
Innovative Co
McGuireWoods LLP
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