WO2009109931A1

WO2009109931A1 - Control and analysis of a solvent exchange process

Info

Publication number: WO2009109931A1
Application number: PCT/IB2009/050901
Authority: WO
Inventors: Michael Stephen Dann
Original assignee: Michael Stephen Dann
Priority date: 2008-03-05
Filing date: 2009-03-05
Publication date: 2009-09-11

Abstract

This invention is concerned with a solvent exchange process and the apparatus therefore wherein a probe carrying a series of pairs of sensors provided along the lengths of the probe is used to enable the electrical resistivity of the material being subjected to the exchange process and into which the probe is immersed to be determined at various locations and between pairs of sensors repetitively at predetermined intervals with this resistivity used to display the state of or the change of state of the constituents of the material.

Description

CONTROL AND ANALYSIS OF A SOLVENT EXCHANGE PROCESS

FIELD OF THE INVENTION

This invention relates to the control and analysis of a solvent exchange process from information extracted from the process during operation.

BACKGROUND TO THE INVENTION

Solvent exchange is a well known and widely used process in the pharmaceutical, food and beverage, petrochemical, environmental, biotechnology, nuclear and metallurgical industries.

The continuous process requires mixtures and separation of chemically reacting constituents and control and recovery of end products and reaction materials.

The process is generally controlled by visual observations, limited measurements and sampling, and the experience of operators.

OBJECT OF THE INVENTION

It is the object of this invention to provide a method and means for extracting information of conditions existing during a solvent exchange process affording useful analysis material and control indications.

SUMMARY OF THE INVENTION

According to this invention there is provided a method recording conditions occurring within a solvent exchange process comprising controlled measurement of electrical resistivity at intervals and locations through the depth of the reacting fluid or solid constituents and recording variation of resistivity with the time to establish the occurrence of changed state of the constituents within the depth of the liquid. The method further provides for the use of the information derived from the measurement for analytical and control purposes in optimizing the operation and understanding of the exchange process.

The invention also provides the means for obtaining the above recordal comprising a probe supporting a series of pairs of electrical sensors along its length and connected into circuits adapted to provide timed application of electrical power to the sensors, recordal of resistivity at different positions along the probe and changes in the location of selected resistance within the surrounding mixture of solids and/or liquids with time.

Further features of the invention provide for the probe to be connected to a computer empowered by electronic sampling, a smoothing protocol and algorithm with appropriate computer software or to be used in a self-contained industrial instrument.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will become apparent from the following non- limiting example described below wherein reference is made to the accompanying drawings.

Figure 1 is an illustration showing the active sensing probe in a multi-phase solvent exchange process with typical resistances which could be measured.

Figure 2 shows a typical computer screen display for the operation of the laboratory instrument version. This is very similar to the configuration display of the stand-alone industrial version.

Figure 3 illustrates the separation of the phases in a uranium-amine system used to produce the screen display of figure 2.

Figure 4 shows the internal operation of the active sensing probe with typical signal routing to the sensing pins and the bi-phase measurement of resistance between the pins.

Figure 5 shows the components making up the laboratory measurement system.

Figure 6 illustrates the industrial instrument for plant use. Figure 7 shows typical resistivity vs time in a multiphase system with froth and sediment.

DETAILED DESCRIPTION OF THE INVENTION

This kind of information compared to known determinations from physical observations is used to enable improved control of environmental and operating variables to be obtained. This in turn allows control over the productivity obtained from the solvent exchange by control of the flow paths for the separated phases of the constituents.

The two implementations of the device are as a laboratory instrument used with a computer and ancillary equipment or as an industrial plant instrument which is "self- contained".

The basic principles of operation are the same for both styles of device with some additional computation, experiment control and interpretation provided in the laboratory version.

Figure 1 shows the active sensing probe (1 ) as an elongated rectangular rod immersed in a medium (2) with a series of odd numbered sensor pins (3) down one edge and even numbered sensors (4) symmetrically interspersed down the other edge. These sensors shown in equivalent circuit diagram form in figure 2 are shown down each side of the active sensing probe, odd numbers (6) down one side and even numbered (7) on the other side. A switching arrangement connects up the sensors in sequence so that the current flows out one sensor, into another and then though the selected shunt resistor (9).

The resistivity of the liquid is measured in this way with the current polarity being reversed for a repeat measurement with the opposite polarity. The average of these measurements is used to calculate the resistivity of the surrounding medium between the selected sensors.

There are many sensors along the length of the active sensing probe so that the patterns of resistivity between each pair of sensors can be used for display or for monitoring purposes for predetermined conditions to occur in the surrounding medium in which the probe (1 ) is operatively submerged or embedded.

The probe (1 ) carries a series of pairs of electrical sensors (3) and (4) spaced apart at distances which can be from about 0.1 to 100 mm or more. The pairs are connected so that the resistance between each pair of sensors can be determined. These sensors (3) and (4) are connected into an electrical circuit which can produce several output signals and the values can be read out from the probe. The operation is cyclic at given time intervals. Where desired the sensors of each pair may be displaced along the length of the probe (1 ).

The signals of resistivity received from the probe (1 ) can be electronically converted through a computer into visual information and electrical control signals which will indicate any changes in the constituents of the solvent liquid medium. Such non-conformities will indicate interfaces in the liquid and their change with time. The time intervals may be for example to set at one reading per second to one hundredth of a second. This will determine the cyclic time for each complete recording of resistivity down the length of the probe.

The visual representations suitably obtained through the computer which can be either internal or external to the probe, will result in a profile of resistivity along the length of the probe (6) in Figure 3.

Figure 3 illustrates a typical display of the measurements from the probe. The resistance profile graph (6) is measured continuously and from this using a constant resistance intercept (watchline), the fixed resistance position graph (7) can be obtained.

Such a representation gives information on changes which can indicate the different layers of constituents within the mixture during a settling period or continuously.

Electronically tracking a particular resistivity recorded against time over multiple cycles enables the profile or thickness of a band of constituents against time such as indicated as (7) to be obtained.

Thus from figure 7, a graphic representation as shown in the drawings, the display of resistivity against time indicates initial readings (30) which change and could mean the depositing of solids (sediment) (31 ), followed by a steady state in the constituents during reaction (32). Thereafter a further change which will indicate an interface at between aqueous- and organic- (or any other) phases in the constituents or surrounding medium.

Under different conditions the information from graphic representations similarly obtained can represent other phenomena including a settling phase, separation in multi-phase liquids, inter-phase layers, formations of sediments of or froths and properties thereof. Still other phenomena can be indicated such as for example bacterial growth.

The probe and its use can be undertaken in tests, say, for determining the efficiency of reagents used in the exchange process.

In the laboratory instrument case, the system shown in figure 5 is computer assisted, with a sequence of step by step procedures which can be tailored to requirements.

The apparatus consist essentially of a measurement chamber (10) in which is mounted the probe (1 1 ). The chamber (10) is connected to a circulator and pump (13) and water bath (12).

A stirrer assembly (16), a funnel (15) for the introduction of reagent and temperature sensor (14) are mounted above the chamber (10). Electrical instrumentation is connected to an interface unit (18) coupled to a computer (17) using any interface method, USB, RS232, ethernet or any other method. The computer also has an RS232 connection to the stirrer (16) assembly. From these components data in readable form can be obtained and used in test procedures.

Aqueous and organic continuous operation can be used with automated stirrer control. Report generation and Excel compatible data files are produced with the saving of "Test Procedures" for rapid and repeatable testing. The results can be printed out as the experiment is completed or saved to a PDF file and printed out at any time.

An Excel compatible CSV result file is generated with complete experimental test procedure and reagent details. pH, redox are optional inputs. The useful "Replay" function can be used to analyze data captured previously using different analysis parameters. The system provides a flexible configuration to suit different particular test and research requirements.

The measurement chamber (10) in figure 5 serves as a stirred one litre vessel that functions as a mixing vessel, and once the stirring is stopped, as a settler. It also has sampling ports, bottom discharge and a glass sleeve for temperature control when attached to a warm bath. The bottom discharge allows it to be used like a separation funnel. In essence, all standard solvent exchange equilibrium, kinetic and phase disengagement test (5) can be performed in this vessel under tightly controlled conditions and with good repeatability.

This probe (1 1 ) is equipped with multiple resistivity measuring points, each measuring resistance at a different height in the vessel, and at intervals of 10OmS or less.

As the aqueous phase is highly conductive, and the organic phase non-conductive, their relative depths are detected by the active sensing probe (1 1 ).

As the settling commences, the probe provides an accurate measurement of phase disengagement, and as it is recorded on the computer, there is no need for optical measurements on the internal scale, use of stopwatches or cameras.

The dispersed phase is indicated by measurable "noise" on measurement probe, and the nature of the interface, the presence and depth of any third phase, the presence and depth of crud, can all be measured scientifically.

As the stirrer is fully programmable, the speed stirring time, cycles etc. can be pre-set and are repeatable.

The present invention also provides the required repeatability and accuracy as it automates many subjective steps currently done by an operator. Furthermore, it provides additional, valuable data on the phase disengagement characteristics, characterization of crud, and plant troubleshooting.

The measurement of a number of standard parameters in copper solvent exchange process differ between reagent suppliers. The method described here provides a level of impartially, comparison and repeatability in reagent testing.

In the self-contained industrial instrument case illustrated in figure 6, the various computations and resistance tracking is done internally and inside the control and display unit (19). The instrument can produce one or more output signals (26) based upon measurements derived from the resistance measurements. Configuration and setting up of this instrument is done using a very similar software interface which also allows the various resistance profiles and other derived graphs to be displayed. Figure 6 illustrates the operation of the self-contained industrial instrument in a multiphase medium (21 ) into which the probe (20) has been immersed with examples of various resistance profiles (24) and (25). The constant resistance intercept (23) intersects the resistance profile measured and from the intersection point an output signal can be derived. This output signal is changed as the intersection point changes from (24) to (25) in figure 6 due to changes in the surrounding medium (21 ). Several constant resistance intercepts can be used to derive more than one output signal.

In addition to this, output signals can be derived simply from the measured resistivity between any two selected sensing pins.

This invention thus provides a novel multi-point conductivity probe (4) linked to suitable electronic sampling and smoothing protocol and algorithm, together with appropriate customized computer software. The probe (4) is utilized to generate the data. Using continuous on-line measurements of resistivity, and therefore the conductivity, the characterization of phase separation of aqueous- and organic- fractions in solvent- exchange applications is possible. A kinetic profile is generated, and the completion of the phase-separation process determined electronically. The presence of crud, stable emulsions, or third-phase formation can also be detected.

The invention allows cyclic electrical resistivity measurements to be used to analyze a useful representation of phase separation and related parameters in solvent exchange processes. The information can be related to operational features to reproduce the exchange process and continuous readings matched against those operational features to ensure effective production from any particular exchange plant.

Claims

1 . A method of recording conditions occurring within a solvent exchange process comprising controlled measurement of electrical resistivity at time intervals and locations through the depth of the reacting fluid constituents and recording variation of resistivity with the time to establish the occurrence of changed state of the constituents within the depth of the liquid.

2. A method as claimed in claim 1 in which the recorded conditions are used for analytical purposes to derive understanding of the exchange process.

3. A method as claimed in claim 1 or 2 in which the recorded conditions are used for control purpose to optimize the operation of the exchange process.

4. A probe for controlled measurements of electrical resistivity within a solvent exchange mixture process comprising an elongated bar for insertion into the exchange mixture and supporting a series of pairs of electrical sensors connected into a circuit adapted to provide timed application of electrical power between selected sensors and recordal of the resistivity at different positions along the length of the probe at timed intervals.

5. A probe as claimed in claim 4 included in laboratory apparatus having a measurement chamber in which the probe is mounted and having means for stirring a solvent exchange mixture in the chamber, means for the controlled introduction of reagents into the chamber, and an external computer means for receiving signals from the probe and converting the signals into readable format.

6. A probe as claimed in claim 4 including computer means for receiving signals of resistivity measurements from the probe sensors and for converting these signals into controls for the solvent exchange process.

7. A probe as claimed in claim 4 or 5 connected to a computer to receive signals from the probe and powered by electronic sampling, a smoothing algorithm with appropriate computer software.

8. A probe substantially as described and illustrated in the accompanying drawings.