US 5,106,468 AGranted

Electrophoretic separation

AssigneeExxon Research & Engineering Co.

InventorRobert J. L. Chimenti

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Abstract

For the electrophoretic separation of a dispersed phase or contaminant (solid, liquid, or gaseous) from a continuous liquid phase under conditions of intrinsic ionic conductivity due to intrinsic bipolar ions in the continuous phase, especially for conductivities of the continuous liquid phase in excess of about 10.sup.-8 (.OMEGA..m).sup.-1 for which known electrofiltration processes are relatively ineffective or unworkable, a voltage is applied to the dispersed phase-containing liquid phase. The dispersed phase has a field-dependent mobility, and the applied voltage is such as to establish, within the liquid to be treated, a periodic asymmetric electric field E(t), conveniently comprising alternate positive and negative rectangular pulses, having the properties that the time-averaged amplitude of E(t) over one complete period, T, is zero but the average amplitude of each positive feature of the periodic waveform is unequal to that of each negative feature. These conditions give rise to a net electrophoretic migration of dispersed phase which causes dispersed phase to accumulate in a collection region, for example on one or more collector surfaces or within the liquid bulk. In the former case, the collector surfaces are periodically cleaned or regenerated (for deposited solids) or, for liquid or gaseous contaminants, the dispersed phase separates by settling or floatation from the collector surfaces. In the latter case the collected dispersed phase can be mechanically filtered off (with a solid dispersed phase) or allowed to settle or float (for solid, liquid or gaseous dispersed phases). The process is of particular practical importance for the electrofiltration of contaminated petroleum liquids.

Claims16

Dependent claims

A method of effecting separation, by electrophoresis, of a dispersed phase in a continuous liquid phase under conditions of intrinsic ionic conductivity due to intrinsic bipolar ions in the continuous phase, said dispersed phase exhibiting a field-dependent mobility .mu.(E) when the dispersed phase-containing continuous phase is subjected in a treatment zone to an applied periodic voltage which produces an electrophoretic migration of the dispersed phase in the continuous liquid phase, which voltage causes both the continuous liquid phase and the dispersed phase to be subjected to an electric field, E.sub.in (t), within the continuous liquid phase, where t represents time, having a periodic waveform of period T, said mobility .mu.(E) being defined as the ratio, at any instant, of the dispersed phase electrophoretic migration velocity to the electric field E.sub.in (t), wherein the electric field E.sub.in (t) is defined by the equation, E.sub.in (t)=E.sub.o +E(t), where E.sub.o is a constant electric field of one polarity which may be zero and E(t) is an electric field component having an asymmetric periodic waveform of alternate positive and negative features, where "asymmetric periodic waveform" is defined for E(t) by the conditions ##EQU33## where t.sub.o is the time at which any arbitrary feature of one polarity commences and T.sub.H and T.sub.L are the time durations of the positive and negative features, respectively, where T.sub.H +T.sub.L =T, said electric field component interacting with said bipolar ions to produce said field-dependent mobility for effecting said migration, said migration directly causing an asymmetry in the population of the dispersed phase in the continuous liquid phase, said method further comprising effecting a relative separation as between on the one hand at least dispersed phase in a region of said continuous liquid phase having a relatively high dispersed phase amount due to said population asymmetry and on the other hand continuous liquid phase in a region of relatively low dispersed phase amount.

Apparatus for effecting separation, by electrophoresis, of a dispersed phase in a continuous liquid phase under conditions of intrinsic ionic conductivity due to intrinsic bipolar ions in the continuous liquid phase, said dispersed phase exhibiting a field-dependent mobility .mu.(E) when the treatment zone to an applied periodic voltage which produces electrophoretic migration of the dispersed phase within the continuous liquid phase, said voltage having a waveform of period T, said mobility .mu.(E) being defined as the ratio, at any instant, of the dispersed phase electrophoretic migration velocity to the electric field E.sub.in (t) acting on the dispersed phase, said apparatus comprising:

(i) means for handling a quantity of dispersed phase-containing liquid;
(ii) means for applying a voltage to the dispersed phase-containing liquid phase such that both the continuous liquid phase and the dispersed phase experience an electric field E.sub.in (t) which is defined by the equation E.sub.in (t)=E(t), where E.sub.o is a constant electric field of one polarity which may be zero and E(t) is an electric field component having an asymmetric periodic waveform of alternate positive and negative features where "asymmetric periodic waveform" is defined by the conditions ##EQU34## where t.sub.o is the time at which any arbitrary feature of one polarity commences and T.sub.H and T.sub.L are the time durations of the positive and negative features, respectively, where T.sub.H +T.sub.L =T, said electric field component E(t) interacting with said bipolar ions to produce said field-dependent mobility .mu.(E) so as to produce said electrophoretic migration, said migration directly causing an asymmetry in the population of the dispersed phase in the continuous liquid phase;
and
(iii) means for effecting a relative separation as between on the one hand at least dispersed phase in a region within said continuous liquid phase handling means containing a relatively high amount of dispersed phase due to said population asymmetry and on the other hand continuous liquid phase in a region within said continuous liquid phase handling means containing a relatively low amount of dispersed phase.

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Dependencies are inferred from the claim text.