Liquid purification or separation – With heater or heat exchanger – Flow line connected in series with distinct separator
Patent
1986-11-12
1988-11-15
Spear, Frank
Liquid purification or separation
With heater or heat exchanger
Flow line connected in series with distinct separator
210315, 210489, B01D 3502
Patent
active
047847662
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to pressure crystallization equipment for causing a liquid to become solid at high pressures, such as 500 atms or more, and more particularly to equipment for use in solidifying a liquid content under such high pressures and separating it in the form of a solid from the mother liquid mixture.
BACKGROUND OF THE INVENTION
When two or more substances are present in a liquid state or in a slurry state (hereinafter referred to as the liquid mixture), there have been many chemical methods for separating a particular content from the other contents. However, the conventional methods are not effective to separate one particular content from others when the contents are eutectic or form a solid solution, where the contents are so similar in chemical and physical properties that they are difficult to separate. As a result the common practice is to effect the separation of contents at particular temperatures, which will be referred to as cooling crystallization. This includes a cooling method under which a particular content is separated at its freezing point from the others.
However cooling crystallization has some disadvantages; for example, (1) it is difficult to control the temperature, (2) temperature gradients are likely to occur in the system, thereby preventing the achievement of thermal equilibrium and (3) the operational time is prolonged.
Therefore the inventors have started to solve the problems encountered in cooling crystallization and have developed a crystallization process utilizing pressure instead of heat, hereinafter referred to as pressure crystallization equipment.
As the pressure crystallization method is operated for commercial purposes, particularly using large-scale equipment, new problems have arisen. One of them is how to discharge the liquid phase out of the system under a high pressure when the liquid and solid phases co-exist as a mixture therein.
Under the pressure crystallization method with the rise in pressure the crystallization proceeds, whereas as the pressure is decreased the crystals melt or become soft. As equipment a cylindrical highpressure vessel is used, which is provided with a filter on its inside wall. Behind the filter the system is communicated with the atmosphere wherein the communication is blocked by means of a valve when it is intended to allow liquid and solid phases to co-exist. There are many modifications to it.
In operation a mixture in a liquid state is put in the vessel; the communication with the atmosphere is blocked and the discharge of a liquid is closed, which means that the vessel is completely closed. A high pressure is applied to the mixture in the vessel; if necessary, the temperature is reduced. In this way the particular content is crystallized in the mixture, thereby producing a state in which the particular fraction of crystals and the remaining liquid co-exist. Then the valve is opened so as to withdraw the liquid content, which is forced out through the filter by applying pressure to the mixture in the vessel. The pressure is continuously applied to the remaining solid phase so as to squeeze it and force the remaining liquid through the filter. In this way a highly pure content remains in the vessel.
Reference will be made to FIG. 1, which shows an example of a conventional high-pressure vessel. The vessel 1 has as filter 2, a thermal insulating material 3, a piston 4, a bottom closure 5, a mixture supply pipe 6, and a discharge pipe 7.
The steps taken to operate the illustrated vessel are as follows: mixture to enter the vessel 1; the piston 4 is caused to descend, thereby causing an increased pressure upon the mixture in the vessel. In this way the crystallization of a particular content is promoted; subsequent filtering and squeezing start; that is, first, the liquid content in the vessel is squeezed, and caused to pass through the filter. The fluid content passes through a path 8, and is discharged through the pipe 7 via the valve V7; and the solid cake at the atmospheric pressure i
REFERENCES:
patent: 1908925 (1933-05-01), Semon et al.
patent: 2346018 (1944-04-01), Fulton
patent: 3190450 (1965-06-01), Stoller et al.
patent: 3201858 (1965-08-01), Valyi
Kitagawa Kazuo
Moritoki Masato
Kabushiki Kaisha Kobe Seiko Sho
Spear Frank
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