Chemical apparatus and process disinfecting – deodorizing – preser – Physical type apparatus – Means separating or dissolving a material constituent
Reexamination Certificate
2001-08-16
2004-03-02
McKane, Elizabeth (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Physical type apparatus
Means separating or dissolving a material constituent
C422S256000, C210S634000, C210S744000, C210S097000, C210S194000, C210S197000, C210S256000, C210S261000, C210S511000
Reexamination Certificate
active
06699445
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to liquid-liquid contacting columns for solvent extraction, stripping, scrubbing, washing, re-extraction and similar operations, and in particular it concerns a liquid-liquid contacting column for effecting multiple operations using a novel intermediate decanter.
It is known that the purpose of liquid-liquid contacting columns for solvent extraction is to recover solute dissolved in one liquid phase, usually an aqueous phase, by extracting the solute with a suitable solvent, usually an organic phase as the other liquid phase, and which becomes the extract. Optionally and typically, the extract is subsequently purified or scrubbed by a suitable scrubbing agent (usually another aqueous phase) to remove undesired contaminants. This unit operation is often followed by a stripping or re-extraction stage in which a suitable stripping agent (usually another aqueous phase) is used to recover the purified product.
In defining a stage as the combined operation of contacting the two participating liquids, allowing them to reach equilibrium by mixing and mechanically separating them by settling, it follows that solvent extraction is, basically, a multi-stage process. Any mixer and settler can be combined to produce one solvent extraction stage, and stages can be arranged in a multi-stage battery.
Many arrangements have been invented in an effort to reduce inter-stage operational volumes, pumping and costs. Some examples are the “Box”-type described by Coplan et al., Chem. Eng. Prog. 50, 403 (1954), or a further modification described by Hazen et al., Min. Eng. 994 (1957), among others.
Other approaches to solvent extraction have been suggested, such as U.S. Pat. No. 3,017,253 to Coleby, which teaches a Graesser extractor that is based on an horizontal shell with a series of buckets revolving around an inner shaft dropping droplets of one liquid through the other.
A more advanced equipment category for solvent extraction allows continuous and differential operation. The equipment in this category is usually arranged for multi-stage, countercurrent contact of the two participating liquids, without complete repeated separation of the liquids between adjacent stages. Instead the liquids remain in continuous contact while flowing through the equipment. Typical examples of this category are the various types of extraction columns.
Countercurrent flow is maintained in the equipment by the difference in densities of the liquids and the force of gravity. Both liquids are pumped through the equipment at any desired linear velocity and selected phase ratio.
In many cases, the density difference between the liquids is insufficient to disperse one liquid in the other and to keep turbulence at the requisite level for efficient mass transfer. Various mechanical stirring or pulsation devices may apply additional energy needed for reaching the desired turbulence. U.S. Pat. No. 2,601,674 to Reman et al., for instance, relates to a rotary disk contactor, which is an example of a mechanical stirred continuous device, while U.S. Pat. No. 2,011,186 to Van Dijk is an example of a pulsed column.
In pulsed columns, a reciprocating motion is applied to the main column cylindrical section to agitate the liquids, provide the desired turbulence and thus improve the rate of mass transfer. Reciprocating plungers or pistons can be used as pulsing devices. A more current approach uses air pulsing devices. Beneath and beyond the extraction column cylindrical section, in which the mass transfer takes place, there are usually placed settling decanters, each of a suitable volume, for proper separation of each of the two liquid phases. The clear light phase flows out the top of the column and the clear heavy phase flows out the bottom.
As described briefly above, solvent extraction is often followed by purifying or scrubbing the extracted phase from undesired contaminants, and by recovering the purified product by stripping. Performing these tasks necessitates at least one, usually more, additional columns, and additional equipment such as settling decanters, holding tanks, pumps, control devices, pulsing means, etc.
Theoretically, appreciable savings in equipment and energy (as well as improvements in process ecology in many applications) could be achieved by building a single column in which multiple process stages are integrated. However, although feeding an extraction column via an intermediately disposed feed port is relatively straightforward, the selective removal of a given phase via an intermediately disposed discharge port is, to the best of our knowledge, unknown in the art, and has certainly not seen widespread commercial implementation. Moreover, to date, there is no known prior art system for and method of, performing several countercurrent operations in series in a single column.
There is therefore a recognized need for, and it would be highly advantageous to have, a system for, and a method of, solvent extraction that has the ability to extract and purify and recover materials in a single, integrated column.
SUMMARY OF THE INVENTION
The present invention is a system for, and a method of, liquid-liquid contacting for performing solvent extraction and stripping, scrubbing and similar additional operations, in a single, integrated column.
According to the teachings of the present invention there is provided an intermediate decanter in a liquid-liquid contacting system. The decanter, disposed between an upper contacting column and a lower contacting column, includes: (a) a housing having: (i) a top opening communicating with the upper column; (ii) a bottom opening communicating with the lower column; and (iii) a decanter outlet designed and configured for discharging a substantially heavy phase. The intermediate decanter further includes: (b) a first partition within the housing forming a first settling chamber and a second settling chamber. The first partition is designed and configured within the housing so as to direct a flow of a substantially light phase received from the lower column through the second settling chamber, wherein the light phase is separated from the heavy phase of the lower column, into the first settling chamber, wherein the light phase is separated from the heavy phase of the upper column. The heavy phase is in communication with the decanter outlet, for discharge thereto, and the light phase is in communication with the upper column, for discharge thereto.
According to another aspect of the present invention there is provided an integrated column for performing a plurality of liquid-liquid contacting functions. The column includes: (a) an upper column section; (b) a lower column section, and (c) an intermediate decanter fluidly connecting between the upper column section and the lower column section. The intermediate decanter includes: (i) a housing having: (A) a top opening communicating with the upper column section; (B) a bottom opening communicating with the lower column section, and (C) a decanter outlet designed and configured for discharging a substantially heavy phase therefrom. The intermediate decanter further includes: (ii) an inner workings including: a first partition designed and configured within the housing so as to form a first settling chamber and a second settling chamber, and so as to direct a flow of a substantially light phase received from the lower column section through the second settling chamber, wherein the light phase is separated from the heavy phase of the lower column section, and into the first settling chamber. In the first settling chamber the light phase is separated from the heavy phase of the upper column section and discharged through to the upper column section, while the heavy phase is discharged though the decanter outlet.
According to yet another aspect of the present invention there is provided an integrated column for performing a plurality of liquid-liquid contacting functions. The column includes a plurality of units, each including: (a) a column section, and (b) an intermedi
Bateman Advanced Technologies Ltd.
Friedman Mark M.
McKane Elizabeth
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