Food or edible material: processes – compositions – and products – Processes – Cooling – freezing – or treating cooled or frozen product,...
Reexamination Certificate
2000-04-19
2001-09-04
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Cooling, freezing, or treating cooled or frozen product,...
C062S052100, C062S064000, C099S517000, C426S519000
Reexamination Certificate
active
06284302
ABSTRACT:
BACKGROUND OF INVENTION
The invention relates to a process and an apparatus for cooling and atomizing liquid or pasty substances.
Cooling processes are used to change the product properties of substances. The substances to be cooled are generally treated in apparatuses whose cooling action is based on heat-transfer processes between a coolant and the substance to be cooled at cooling surfaces. The heat or cold transport between coolant and the substance to be cooled is therefore only indirect. A relatively rapid cooling of the substances, which is frequently required, cannot be achieved by this means. These cooling processes are also frequently unsuitable for carrying out a crystallization or a freezing, since insulating deposits form on the cooling surfaces which can impair the cooling process. Cooling processes of this type are, for example, described in Römpp Chemielexikon [Chemistry lexicon] and Pahlmann, Taschenbuch der Kältetechnik [Refrigeration manual].
It is further known that on an industrial level, spraying towers are used to produce pulverulent products with the use of conventional refrigeration.
Cryogenic cooling and freezing processes in which low-temperature gases are used are also prior art. Römpp Chemielexikon and Pahlmann, Taschenbuch der Kältetechnik, for example, disclose processes in which the substances to be cooled are sprayed with the refrigerant, in particular with liquid nitrogen or with solid carbon dioxide in the form of dry ice or snow. The direct contact of the refrigerant with the substances leads to a substantially more rapid cooling of the substances than with the abovementioned conventional processes. For a relatively rapid cooling of liquid or pasty substances this process also is unsuitable, since the cooling in the interior of the substances is determined by the heat transport through the substance itself, and the contact surfaces for a rapid cooling, for example for crystallization, are still too small. It is virtually impossible with these processes to produce readily meterable flowable substances.
The Cryopel® process, described in U.S. Pat. No. 4,967,571, the Cryobreak® process, described in DE 44 19 010 C1 and the Cryofals® process, described in DE 43 29 110 C1, are known processes in which liquid substances are cooled very rapidly by being introduced dropwise into liquid nitrogen. This cooling process can lead to a meterable pelleted substance. The particle sizes which are established are generally in the range of a few millimeters. The cooling is always performed to the temperature of the liquid nitrogen of approximately 77 K, which is not necessary or even undesirable in a multiplicity of applications.
In addition, an apparatus is known in which a liquid substance is brought into contact with liquid nitrogen, with the use of two-jet nozzles, in order to cool the substance rapidly. There is the disadvantage here that the product can be cooled as early as in the nozzle by the low-temperature nitrogen and can block this nozzle.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is to provide a process and an apparatus by which the disadvantages of the prior art are overcome and by which a relatively rapid cooling and atomization of liquid or pasty substances is possible, in particular even relatively small amounts of the liquid or pasty substances being able to be cooled and atomized economically.
The object is achieved by a process in which liquid or pasty substances or mixtures of substances are cooled and atomized in which the liquid or pasty substance/mixture of substances is combined with liquid or super-critical carbon dioxide and then the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide is expanded. The process is carried out in such a manner that the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide is not expanded until on exit from the expansion apparatus. By means of this process, a very direct contact of the liquid or pasty substance/mixture of substances with the liquid or supercritical carbon dioxide is achieved. The carbon dioxide snow produced by the expansion (Joule-Thompson effect) or the gaseous carbon dioxide has a temperature of approximately 195 K, as a result of which the liquid or pasty substance/mixture of substances is cooled rapidly and instantaneously.
In the expansion, relatively small particles of the liquid or pasty substance/mixture of substances are formed. This leads to a finely particulate, relatively easily flowing and thus relatively easily meterable product from the liquid or pasty substance/mixture of substances. A further advantage of the process according to the invention is that by varying the flow ratios of substances/mixtures of substances and liquid or supercritical carbon dioxide, the final temperature which is established may be influenced in broad ranges.
It is envisaged that the liquid or supercritical carbon dioxide has a pressure of from 5 to 500 bar and a temperature of from 216 to 373 K, preferably a pressure of from 10 to 200 bar and a temperature of from 230 to 323 K, and particularly preferably a pressure of from 15 to 80 bar and a temperature of from 248 to 313 K. This produces the advantage that at a preferred pressure range and temperature range the carbon dioxide can be taken off directly from the supply systems, for example low-pressure and medium-pressure tanks or carbon dioxide cylinders, without further gas treatment.
According to the invention the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide is expanded to a pressure from 0 to 60 bar, preferably to a pressure from 0 to 20 bar, and particularly preferably to approximately 1 bar. The expansion to atmospheric pressure (approximately 1 bar) has the advantage that filling can be performed directly into unpressurized systems and the potential cold content of the carbon dioxide can be exploited to the maximum in each case.
According to the invention the liquid or pasty substance/mixture of substances and/or or liquid or supercritical carbon dioxide and/or the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide can be fed to at least one heatable or coolable line. Using a heatable or coolable line, the temperature for the liquid or pasty substance/mixture of substances and/or the liquid or supercritical carbon dioxide and/or the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide can be controlled, in order to set the desired or required process temperature.
The mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide is fed, according to the invention, to a mixer, preferably a static mixer, before it is expanded. As a result, advantageously, an intensive mixing of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide is achieved.
According to the invention the liquid or pasty substance/mixture of substances is mixed with the liquid or supercritical carbon dioxide upstream of the feed into a heat exchanger and/or upstream of the feed into a mixer and/or upstream of the expansion of the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide, or directly in a two-component nozzle for expansion of the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide. Mixing the liquid or pasty substance/mixture of substances with the liquid or supercritical carbon dioxide upstream of the feed into a heat exchanger produces the advantage that undesirable mixing temperatures which adversely affect a component are excluded. If the mixing is performed upstream of the feed into a mixer or directly upstream of the expansion of the mixture of liquid or pasty substance/mixture of substances and liquid or supercritical carbon dioxide, advantageously an intensive mixing of the liquid or pasty su
Berger Thomas
Buschkens Guido
Lingler Klaus
Nobis Peter
Connolly Bove & Lodge & Hutz LLP
Messer Griesheim GmbH
Yeung George C.
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