Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-12-15
2001-07-17
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06262145
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to segregated mixing and phase separation techniques, in particular a method of extraction from multi-phase systems, particularly two-phase systems wherein the phases are fluid, and/or slurry.
BACKGROUND OF THE INVENTION
Many processes require an extraction step in recovering the desired product. In some extraction processes undesirable impurities may be removed from a fluid system while in other extraction processes the product may be removed from the fluid system. Common extraction involves placing a fluid containing the component to be extracted (the extractive component) in direct contact, usually by rapid mixing, with a second fluid (the extraction fluid) which attracts or traps the extractive component, thereby reducing the level of that component in the first fluid. Unfortunately, extraction by conventional methods many times leaves entrained phases of the extraction fluid in the fluid which is being acted upon. These entrained phases contain the very components which are meant to be extracted from the first fluid. As an example, polymerization and hydrogenation of polymer cements requires the use of polymerization initiators and hydrogenation catalyst. Extraction of the initiator and/or catalyst is required to produce a polymer relatively free of metals found in the initiator and/or catalyst. Conventional methods of extraction are to either disperse acids, such as sulfuric or phosphoric acid, into the polymer cement, or to disperse polymer cement into acids, both methods commonly accomplished by rapid mixing for a period of time, followed by allowing the material to settle and separate. Extraction by this conventional method leaves entrained acid phases in the polymer cement. Metal impurities successfully extracted to the acid are thereby returned to and entrapped in the cement when the acid becomes entrained. Further, trapped acid phases reduce extraction efficiency and leave residuals of the acid, such as sulfates or phosphates, in the final polymer product.
Another problem with conventional extraction is that the rapid mixing commonly leads to a “rag layer” upon settling. The rag layer is an emulsification of the first and second fluids that will not separate and has no commercial use; it is a waste of an amount of the desired first fluid. Therefore, it would be desirable to have an extraction technology that achieves high extraction efficiency without leaving other residuals in the final product and which reduces or eliminates wasteful rag layer.
It has surprisingly been found that reduction of the level of mechanical agitation during extraction allows for short-time extraction with substantially no residual contaminates or rag layers. In many instances, total extraction times are reduced from those of conventional methods.
SUMMARY OF THE INVENTION
One embodiment of the invention provides a process for extracting and separating extractive components from fluids. A first fluid containing at least one extractive component and an extraction fluid are added to a vessel, thereby creating a two-phase, two-layer system, wherein the first fluid and the extraction fluid are discrete and the two-phase system has a first fluid/extraction fluid interface. The two-phase system is then agitated wherein the first fluid phase and the extraction fluid phase remain as substantially discrete layers. A means for communication between the first fluid and the extraction fluid is provided. The communication of the phases results in the extractive component being extracted from the first fluid into the extraction fluid. Agitation is stopped and the first fluid is recovered having reduced amounts of the extractive component.
Another embodiment provides a method for extracting and separating impurities from polymer cements. A polymer cement and an acid are added to a vessel, thereby creating a two-phase, two-layer system, wherein the polymer cement and the acid are discrete and the two-phase system has a polymer cement/acid interface. The two-phase system is then agitated at a rate that the polymer cement and the acid remain as substantially discrete layers. A means for communication between the polymer cement and the acid is provided. Agitation is stopped and the polymer cement is recovered having reduced impurities.
A third embodiment provides a method for extracting residues from deprotected polymer cements. Residues in deprotected cements are commonly residuals of deprotection solutions, or hydrogenation catalyst, or both. A deprotected polymer cement and water are added to a vessel, thereby creating a two-phase, two-layer system, wherein the polymer cement and the water are discrete and the two-phase system has a polymer cement/water interface. The two-phase system is then agitated at a rate that the deprotected cement and the water remain as substantially discrete layers. A means for communication between the deprotected cement and the water is provided. Agitation is stopped and the deprotected cement is recovered having reduced residuals.
Another embodiment provides a process for mixing a fluid system while maintaining phase separation. A first fluid and a second fluid are added to a vessel, thereby creating a two-phase, two-layer system, wherein the first fluid and the second fluid are discrete and the two-phase system has a first fluid/second fluid interface. The two-phase system is then agitated at a rate that the first fluid phase and the second fluid phase each are well-mixed but remain as substantially discrete layers.
DETAILED DESCRIPTION OF THE INVENTION
The extraction method described works on any multi-phase fluid system. By fluid is meant fluid or slurry and a multi-phase system may consist of fluid, or slurry, or both. The viscosity of the fluid system merely changes the contact and/or settling time but not the process of the invention Therefore, the extraction process works for low viscosity free-flowing liquors as well as high viscosity slurries as long as the fluid containing the impurities and the extraction fluid are of different densities and remain discrete phases when placed in contact.
To practice the extraction process, a first fluid having at least one extractive component is contained in or is added to a vessel. An extraction fluid is added to the vessel, creating a two-phase system wherein the first fluid and the extraction fluid are discrete and the two-phase system has a first fluid/`extraction fluid interface. The two-phase system is then agitated, or mixed, at a rate that ensures the first fluid phase and the extraction fluid phase remain substantially discrete. This may be accomplished, for example by is lowering the agitating speed. Some communication must take place, however, between the phases in order to allow the extraction fluid to contact trap and extract the extractive component. Communication is best accomplished by using a vessel which contains a baffling system. Four longitudinally oriented baffles placed radially at 90 degree intervals around the inner circumference of the vessel have been found to provide excellent communication between the phases.
It is desirable that each phase be well-mixed during the agitation step. This is accomplished, for example, by rotating at least one impeller on a shaft. A flat blade impeller has been found to provide excellent mixing results while keeping the phases substantially discrete. If more than one impeller is used, the preferred positioning is to have a first impeller located in the first fluid and a second impeller located in the extraction fluid. When one impeller is used, or all impellers are located in the same phase, excellent results have been seen when at least one impeller is located very near the first fluid/extraction fluid interface.
Agitation or mixing is continued for a time to allow extractive components in the first fluid to be extracted into the extraction fluid. The agitation is them stopped. It is preferred that the system be allowed to settle after agitation to allow any extraction fluid in the first fluid to separate from the first flui
Chen Ye-Mon
Schisla David Karl
Winjngaarden Rudolf Jacobus
Michl Paul R.
Shell Oil Company
Steinberg Beverlee G.
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