Surface area generation and droplet size control in solvent extraction systems utilizing high intensity electric fields

• US 4,767,515 A
• Filed: 07/30/1987
• Issued: 08/30/1988
• Est. Priority Date: 07/30/1987
• Status: Expired due to Term

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Department of Energy
• Inventors: Wham, Robert M., Scott, Timothy C.
• Primary Examiner(s): Tufariello, T. M.
• Application Number:
  US07/079,390
• Time in Patent Office: 397 Days
• Field of Search: 204/186, 204/302
• US Class Current: 204/558
• CPC Class Codes: B01D 11/0419 in combination with an electric or magnetic field or with vibrations

Abstract

A method and system for solvent extraction where droplets are shattered by a high intensity electric field. These shattered droplets form a plurality of smaller droplets which have a greater combined surface area than the original droplet. Dispersion, coalescence and phase separation are accomplished in one vessel through the use of the single pulsing high intensity electric field. Electric field conditions are chosen so that simultaneous dispersion and coalescence are taking place in the emulsion formed in the electric field. The electric field creates a large amount of interfacial surface area for solvent extraction when the droplet is disintegrated and is capable of controlling droplet size and thus droplet stability. These operations take place in the presence of a counter current flow of the continuous phase.

Claims

1. A method for solvent extraction comprising the steps of:

introducing droplets of a dispersed phase to a counter-current flow of a continuous phase which droplets have a first surface area and are allowed to free-fall through said continuous phase;

applying a constant high-intensity-pulsed electric field to said original droplets of said dispersed phase so as to shatter said droplets into many smaller droplets to form an emulsion of said smaller droplets in said continuous phase, said smaller droplets having a combined total surface area which is greater than a total surface area of said original droplets;

substantially simultaneously coalescing a plurality of said smaller droplets to reform larger droplets, said larger droplets being stable in said electric field; and

separating said reformed droplets from said emulsion to form a separate phase of said dispersed material.

2. The method of claim 1, wherein said pulsed electric field has a pulse rate of from 20-60 Hz.

3. The method of claim 1, wherein said pulsed electric field has a pulse rate of from 60-120 Hz.

4. The method of claim 1, wherein said dispersed phase comprises conducting droplets and said continuous phase is non-conducting.

5. The method of claim 1, wherein each droplet has a natural oscillation frequency and said pulsed frequency applied is in the vicinity of said natural oscillation frequency.

6. A system for solvent extraction comprising:

a column for transporting a solvent extraction system including a dispersed phase and a continuous phase;

means for introducing droplets of said dispersed phase, each of said droplets having a first surface area, to a counter-current of said continuous phase such that said droplets are allowed to free fall through said continuous phase;

means for applying a constant high intensity-pulsed electric field to said droplets of said dispersed phase so as to shatter said droplets into many smaller droplets, said smaller droplets having a combined total surface area which is greater than a total surface area of said original droplets, which small droplets substantially simultaneously coalesce; and

means for supporting said coalesced particles of said dispersed phase from said continuous phase.

7. The system according to claim 6, wherein said first droplet has a natural oscillating frequency and means are provided for adjusting the pulse frequency of said electric field in the vicinity of said natural oscillating frequency of said droplet.

8. The system according to claim 6, wherein a tapered column is provided through which the droplets travel as they pass through the electric field the tip portion of said tapered column being located at the bottom of said column.