Drying and gas or vapor contact with solids – Process – With nondrying treating of material
Utility Patent
1999-03-01
2001-01-02
Gravini, Stephen (Department: 3749)
Drying and gas or vapor contact with solids
Process
With nondrying treating of material
C034S393000, C034S398000
Utility Patent
active
06167637
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for pressure-dehydrating wet or moist materials. The method and apparatus of the invention are particularly suited for, but not exclusively, the processing of foods and medicines and are also applicable to the water extraction from sludge or other wastes.
The word “pressure-dehydrate” in this specification means squeezing of water by compression.
For dehydration of foods or other moist materials a method is available which simply applies pressure to the material. This method, based on a conventional principle that “dehydration depends on power”, has placed importance on increasing the pressure at which to squeeze the material for higher dehydration efficiency.
With the conventional dehydration method based on pressurization only, however, the dehydration rate for food materials with large contents of water, such as bean jam, is limited to about 60%. A further increase in the pressure does not result in enhanced squeezing nor improved dehydration rate. For this reason, this dehydration rate is currently taken as a limit. If, however, the dehydration rate can be increased further, this will reduce the amount of energy required for drying the products after the dehydration process, making significant contributions to saving thermal energy such as oil and electricity.
Food materials such as bean jam are usually pressurized for dehydration while at elevated temperature immediately after being boiled.
When hot materials are processed as is, however, they remain hot even after undergoing dehydration. Because the food material after dehydration remains hot until it is cooled in a refrigerator or the temperature of the central portion of the lumped material is still high at an initial stage of cooling, putrefying bacteria can grow or the quality of the food material may change deteriorating its taste. Further, a large amount of electric energy is required to cool the hot material down to a predetermined temperature in the refrigerator, giving rise to a problem of increased manufacturing cost.
An example of the conventional hydroextractor is disclosed in U.S. Pat. No. 5,152,213. The hydroextractor of this U.S. patent is of a structure in which a pressure chamber is bounded by a diaphragm over a dehydration chamber to press material in the dehydration chamber by the diaphragm which is expanded by a fluid pressure.
SUMMARY OF THE INVENTION
The invention has an object of providing a dehydrating method capable of reducing energy and cost required to manufacture products.
Another object of the invention is to provide a hydroextractor capable of efficiently implementing the above method.
The present inventors have gropingly studied why 60% is the limit for the dehydration based only on pressurization and what is the obstacle to improving the dehydration rate. According to the result of our examination conducted by breaking open dehydrated cakes which were formed by pressurizing food materials such as bean jam, we have found that there are films of cohesive or coagulative substances, or films of crushed paste-like starch, in the cakes. It has been known from this that the pressurization of the material develops coagulative substance films among material particles, which in turn close and clog passages or escape paths for residual water in the material to hinder the dehydration process.
The invention therefore is intended to break the coagulative substance films to increase the dehydration rate. As for the problems associated with hot food materials, the invention aims at forcibly cooling the material as quickly as possible during the dehydration process to prevent growth of putrefying bacteria and deterioration of quality of the material.
The dehydrating method according to the invention involves crushing the material cake, which has been pressure-dehydrated once, and then dehydrating the crushed cake again by compression.
According to this method, when a material with a high water content, such as beam jam, is compressed, coagulative substance films clogging passages for the residual water develop in the dehydrated cake. Then, when the cake is crumbled, the films are destroyed to form water passages again in the cake. After this, when the crushed cake is again compressed, the residual water in the cake is squeezed out through the passages thus formed.
Hence, when the method of the invention is applied to such materials as beam jam which, during compression, will develop coagulative substance films in the dehydrated cake, the dehydration rate can be increased as compared with that achieved by a conventional method. It is therefore possible to reduce the amount of thermal energy required to heat and dry the dehydrated products, i.e., to reduce the consumption of fossil fuel and electricity, making great contributions to energy conservation. The time and cost required for drying can also be reduced. Furthermore, because the drying time is reduced, the quality degradation of the material can be prevented.
The above method preferably further includes a step of cooling the dehydrated cake while the cake is being crushed. With this, when the heated food material is dehydrated, the material is rapidly cooled at the same time, which can prevent degradation of food quality due to growth of putrefying bacteria and also prevent early deterioration of taste. Where the material is medicine, this method can prevent degradation of quality of nutrients such as vitamins.
It is also preferable that the first dehydration step, the crushing step and the second dehydration step be performed sequentially in one dehydration chamber. This improves the efficiency of the dehydrating operation.
In addition to the conventional constitutional elements, such as a dehydration chamber and means for dehydrating material by compression, the hydroextractor of the invention includes means for crushing the dehydrated cake in the dehydration chamber.
This apparatus can implement the above dehydrating method. Further, the apparatus can perform two dehydration and crushing consecutively in one dehydration chamber, thus improving the efficiency.
The crushing means may comprise rotary blades in the dehydration chamber or may be constructed to inject air for crushing the dehydrated cake. The former can directly contact the dehydrated cake to reliably crumble it, and the latter can perform two actions of cooling and crushing at the same time, thus improving also the problem associated with the high temperature of food materials.
Preferably, the dehydration means includes a pressurization chamber adapted to press a flexible diaphragm member against the material, the crushing means comprises a crushing member in the dehydration chamber and a rotary shaft for the crushing member, and a pipe member for letting the rotary shaft sealingly pass is provided through the center of the diaphragm member. Because the rotary shaft for the crushing member is inserted through but isolated from the pressurization chamber, it can easily and reliably rotate the crushing member in the dehydration chamber from outside the apparatus without being affected by the pressure of the pressurization chamber.
It is preferred that the rotary shaft of the crushing member be provided with injection ports from which to inject compressed air into the dehydration chamber. With this arrangement, the dehydrated cake is subjected not only to the direct contact of the crushing member but also to an air injection force and therefore crushed more finely. The injected air can also cool the dehydrated cake. This can further enhance the dehydration rate and deal with the problems associated with hot materials.
The pipe member is preferably movable to extend into the dehydration chamber as the diaphragm member expands, and receive a side of the expanded portion of the diaphragm member. Because the pipe member receives or supports the expanded portion as the diaphragm member expands, it is possible to prevent a situation that the diaphragm member gets entangled with the rotary shaft of the crushi
Kobayashi Kazuo
Masumoto Norio
Nagase Hyosuke
Nagase Yuuji
Antonelli Terry Stout & Kraus LLP
Gravini Stephen
Nagase Yuuji
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