WO2016079095A1

WO2016079095A1 - Apparatus and method for carrying out fibre-optic measurements in moving liquids

Info

Publication number: WO2016079095A1
Application number: PCT/EP2015/076782
Authority: WO
Inventors: Christoph Janzen; Reinhard Noll; Martinus De Kanter
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.
Priority date: 2014-11-18
Filing date: 2015-11-17
Publication date: 2016-05-26
Also published as: EP3221684A1; DE102014016993B3

Abstract

The present invention relates to an apparatus and a method for carrying out fibre-optic measurements in moving liquids. The apparatus has a measuring probe (1) having a probe body in which a sample volume (1a) is formed, which sample volume has at least one opening (4) for exchanging a liquid sample. A movable mechanical element is arranged on or in the sample volume (1a) and can be used to mechanically close at least one partial volume of the sample volume (1a) in order to form a closed measuring chamber (5). An optical measuring window (7) for coupling optical radiation into and out of the measuring chamber (5) is formed on this closed measuring chamber (5). The probe (1) can be used directly in the liquid (3) to be measured, wherein the mechanical element can be used to form a measuring chamber (5) isolated from the environment and liquid can also be exchanged. The method and the apparatus enable an in-line measurement of particle sizes in moving liquids, for example.

Description

Apparatus and method for carrying out

fiber optic measurements in moving liquids

Technical application

The present invention relates to a

Device and a method for carrying out

fiber optic measurements in moving liquids, in particular for measuring particle sizes in the liquids. The measurement of particle sizes in liquids is of great importance in many technical processes

Importance. Such processes are found in various industrial branches, e.g. in the production of plastics (polymerizations, microgel production, etc.), in the food, cosmetics, paint industry or bioanalytics.

As a standard method for determining the

Particle size in liquids has established, among other things, the dynamic light scattering (DLS: Dynamic Light Scattering). This method is based on an investigation of the diffusion motion of the particles. Thus, small particles show a faster movement than large particles in the liquid. The measuring light scattered on the particles is detected time-resolved and examined with the mathematical method of autocorrelation in order to deduce the size of the detected particles. In one embodiment of this measurement method as a fiber-based backscatter method with small penetration depths (FOQELS technique: Fiber Optic Quasi-Elastic Light Scattering), it is also possible to carry out measurements in liquids with a solids content of up to 40 percent by mass. However, the prerequisite for the use of the DLS method is that the liquid sample is at rest and there is an undisturbed diffusion movement. Since in actively mixed liquids the diffusion movement is usually turbulent

Convective movement is superimposed, no undisturbed, exclusively dependent on the particle size diffusion movement can be measured here. Therefore, the DLS method is not suitable for use in liquids in which macroscopic convection currents - triggered by pressure and pressure

Temperature gradients or stirring mechanisms - present. In this case, so far samples for process and quality control have to be taken out of the running process and analyzed offline.

State of the art

Currently, various optical methods are used to measure particle sizes. Established measuring methods for particle size determination in

Liquids represent the static and dynamic

Light scattering. Typically, liquid ^{samples are} illuminated in a cuvette with a laser beam and the light scattered on the particles is examined with time or angle resolution. The samples may only have a low concentration of particles, otherwise multiple scattering and thus falsified measurement results may occur. Novel fiber-based methods of dynamic light scattering use the light backscattered in 160 ° or 180 ° to determine the particle size. Particle sizes in concentration ranges up to 40 percent by mass can be determined. So shows

For example, DE 3719806 AI a fiber optic sensor for measuring according to the principle of quasi-elastic backscattering. As stated above, these methods require a quiescent fluid to take measurements. A moving liquid

The self-movement of the particles (diffusion) superimposes an external flow movement (convection), so that erroneous particle sizes would be determined. Other methods, such as light diffractometry, use the diffraction of particles to determine their size by means of Fraunhofer diffraction and Mie theory. This method is a transmitted light method and therefore only suitable for diluted samples. The particle size determination by means of microscope and image processing also requires diluted samples, since here individualized particles must be available for characterization. In principle, this method is not suitable for particles smaller than the optical resolution of the microscope used.

However, the previously known methods are not suitable for in-situ or in-line measurement in an actively mixed liquid, as e.g. for inline monitoring of particle growth during a chemical polymerization reaction in a sample vessel with stirrers is necessary. To measure the

Particle size must be so far during the process Samples are drawn or separated from the process via a bypass. Analysis of samples is employed, depending on the measurement method requires additional steps for sample preparation ^¬, for example, a dilution of the sample. Subsequently, the sample is analyzed in a separate device. Depending on the complexity of the Probenauf ^¬ preparation for the measurements they find considerable delay instead of the process Phase. A direct one

Feedback to the process control is thus difficult or even impossible. Optimization potential of the process ^¬ guides can not be used with appropriate ^¬ speaking negative impact on process efficiency, cycle times and product quality. In particular for the tracking of time-critical processes, an in-line analysis would be of great advantage for process and quality control, in which it is possible to dispense with taking the sample material out of the process. From US 5956139 A are a system and a

Method for measuring particle sizes in

stationary fluids known in which the

Influence of multiple scattering can be reduced, so that also liquids with higher particle concentrations can be measured. For this purpose, a cuvette with a particle-containing liquid ^¬ keitsprobe is immersed in a vessel with an index-matching liquid. From outside the vessel

irradiated laser light gets on the particles

scattered and detected by means of two arranged outside the vessel detectors whose signals are subjected to cross-correlation. WO 2014/144868 AI shows an optical

Flow cell for flow cytometry, which simultaneously detects Coulter parameters (volume and / or electrical conductivity) and optical properties while pumping a sample to be tested through the flow cell.

The object of the present invention is to provide a device and a method for

Conducting fiber optic measurements in moving

Specify liquids that are directly in the

moving liquid and does not require time-consuming sampling.

In particular, the device and the

Method for dynamic scattered light measurements in

Liquids with convection currents are suitable.

Presentation of the invention

The task is with the device and the

Process according to claims 1 and 9 solved.

Advantageous embodiments of the device and the method are the subject of the dependent patent claims ^¬ or can be the following

Description and the exemplary embodiment.

The proposed device has a

Measuring probe with a probe body in which a

Sample volume is formed, which has at least one opening for an exchange of a liquid sample with the surrounding or surrounding liquid. On or in the sample volume, a movable mechanical element is placed, mechanically completed by the at least a portion ^¬ volume of the sample volume can be used to form a closed measuring chamber. With appropriate design of the mechanical

Elementes also several closed measuring chambers can be formed in the sample volume. The probe body has in this case at the one or more measuring chambers

at least one optical measuring window for input and output

Extraction of optical radiation into or out of the

Measuring chamber on. In a preferred embodiment that is

Cylindrical sample volume and divided by a rotatable in the sample volume rotating element in at least two by the rotation element completely separate from each other sub-volumes. The rotation element is in this case rotatable about the cylinder axis of the cylindrical sample volume and can be set in rotation by a drive provided for this purpose. Of the partial volumes of the sample volume which are separated from one another by the rotary element, one or more are completely closed in at least one rotary position of the rotary element and thereby form the closed measuring chamber (s).

The operation of the proposed device will be explained in more detail below with reference to the preferred embodiment with a rotary member as a mechanical element. It can also come other mechanical elements are used in place of the rotary ^¬ element but, for example, a mechanical element like a drawer, which is the measuring chamber for the formation of (n) is pushed with a suitable drive in the sample volume. The probe of the proposed device is immersed in the moving liquid to be measured to perform the fiber optic measurements. By rotation of the rotary element while liquid is transported from the immediate vicinity via the opening in the sample volume. Upon reaching the at least one position of the rotation element with the closed or the measuring chambers, the rotation element is stopped. As a result, the enclosed liquid sample comes to rest after a short time and can be measured via a fiber-optic coupling through the measuring window (s). Subsequently, the Rotationsele ^¬ ment is returned to rotation, so that the liquid ^¬ keitsprobe is exchanged in the one or more measuring chambers through the opening of the sample volume. Subsequently, a new measurement can begin with fresh sample material.

The proposed device thus provides in moving liquids one or more temporarily closed or encapsulated by the environment

Measuring chambers are available in which fiber optic

Measurements, such as dynamic light scattering (DLS) can be performed. The liquid ^¬ keitsprobe is not removed from the respective process vessel, such as a fermenter, a reaction vessel or the like. Rather, it is isolated by the probe only for a short period of time from the moving medium. This is not an at-line or offline technique, but an in-line technique. The sample in the closed partial volume or the closed measuring chamber can be measured at freely set time intervals and quickly and be exchanged efficiently with the external fluid.

The replacement of the liquid sample can be carried out at variably adjustable time intervals with the outer, moving liquid. The exchange of

Liquid is complete and free of dead ^¬ volumes so that the liquid in the encapsulated measuring volume always corresponds to the composition of the liquid in the surrounding active mixed liquid volume. Particle accumulation in the sample volume is thus also prevented.

In the measuring chamber (s), e.g. Measurements can be performed with dynamic light scattering. An exemplary application of the device is to measure particle size using a 180 ° backscatter DLS probe within a chemical reactor during the synthesis of microgels. Likewise, there is the possibility of simultaneously creating a plurality of mutually delimited measuring chambers by appropriate design of the rotary element and thereby also to use several measuring methods in the device at the same time. Thus, for example, simultaneous

Measurements are made without mutual interference in the individual measuring chambers.

The area encapsulated by the moving liquid, ie the individual measuring chamber, preferably has only a volume of between 100 and 1000 μΐ. At such small volumes, the convective motion of the fluid quickly fades and the fluid settles, causing diffusion to occur shortly after Standstill of the rotating element can be measured trouble-free.

The one or more optical fibers for

Implementation of the fiber optic measurements can be coupled in the proposed device either via arranged on the probe fiber coupler or are directly as part of the device with the

Probe body connected. Between the respective

Junction or the fiber terminal and the associated optical measurement windows are preferably suitable optical elements on or in the probe body ^¬ arranged, through which the fiber from the light emerging from ^¬ colli- mized by the measuring window passes or is focused. That in the measurement

backscattered light is then also on the

Fiber (s) again out of the liquid to be measured and detected in a known manner and evaluated ^¬ .

Preferably also located on the measuring probe and the rotary drive for the rotary member.

This drive can be connected via an axis directly to the rotation element. The supply lines for power supply and control of the drive are guided together with the optical fibers from the liquid to be measured. In principle, however, other drive mechanisms are possible with which such a rotation element can be set in rotation and also stopped again.

In the proposed method, the probe of the proposed device in the submerged measuring liquid. The rotation ^¬ element is set in motion in order to convey a liquid ^¬ keitsprobe in the measuring chamber (s).

Subsequently, the movement of the rotation element is stopped, so that the measuring chambers are encapsulated by the surrounding liquid. After a short

Time interval, a corresponding fiber optic measurement in the or the measuring chambers on the or the measurement window is performed. Subsequently, the

Rotation element is set in motion again, so that the liquid is exchanged. Subsequently, a new measurement is carried out with the volume of liquid newly introduced into the measuring chambers. This procedure can be repeated as often as you like. The

Frequency of the measurements is adapted to the respective application. By using the proposed

Device, the measurement can be done directly in each liquid to be measured. A removal of a sample from the liquid is not required.

The method and the device thus enable the in-situ or in-line measurement of the particle size using fiber-optic measurement techniques, in particular by means of DLS. This is e.g. given the opportunity to determine particle sizes within a chemical reactor with the aid of a 180 ° backscatter DLS measurement. Further processing is not required and the reaction processes and particle formation can be followed directly. Also a measurement in channels or pipes is possible. Of course that is

Method and apparatus are not limited to such an application, but can be used in all technical fields in which fiber optic Measurements in moving liquids should be carried out.

Brief description of the drawings

The proposed device and the pre- ^¬ proposed method will be explained in more detail using an exemplary embodiment in conjunction with the drawings. Hereby shows:

Fig. 1 is a schematic representation of an exemplary embodiment of the proposed ^¬

Contraption .

Ways to carry out the invention

The proposed invention is based, with a rotating element, in the present example an impeller which is rotatable in a cylindrical sample volume of a probe with, for example, cylindrical probe body, temporarily to form one or more of the environment delimited measuring chambers. In the outer wall of the probe body is located

at least one opening to the sample volume, through which the surrounding liquid can flow in and out. The probe is immersed in the turbulent by ^¬ mixed liquid to be analyzed. By rotation of the vane ^¬ wheel replacement of the liquid takes place inside the probe with the outer volume. When the impeller is stationary, the liquid is inside the probe, ie in the

Sample volume, isolated from the turbulent fluid movement in the outer space and comes to rest, so that, for example, DLS measurements are possible. at

Use of an impeller with three or more blades can also produce several closed measuring chambers In which different optical analysis methods, for example a scattered light measurement for analysis of particle sizes and a Raman measurement for the analysis of chemical compositions, can be combined in the probe. Since the individual measuring chambers light-tight by the impeller preferably separated from one another, the various optical measuring operations can be performed simultaneously without mutual interference by ^¬.

An increased rotation frequency of the impeller can be used to clean the sample volume and the effective

Replacement of the sample liquid can be used.

Unless samples are examined, referring to the optical measurement windows through which the measurements

can take place, settling and thereby clouding, the impeller on the window side with a

Wiper lip are provided, which causes a mechanical cleaning of the window or the windows during rotation. Alternatively or additionally, over

At least one piezoelectric element and an ultrasonic ^¬ vibration are transmitted to the probe body to support the cleaning. Figure 1 shows an example of a possible

Embodiment of the device. The device is designed as a measuring probe 1 with a cylindrical probe body and intended to be immersed in a container, for example a reactor 2, with liquid 3 in which the measurements are to take place. The cylindrical probe body of the measuring probe 1 has a cylindrical cavity as the sample volume 1a, in which a multi-winged rotor 6 is rotatably mounted. Via one or more openings 4 in the outer wall of the cylindrical probe body of the measuring probe 1, the liquid to be measured passes into the sample volume 1 a, which is subdivided by the wings of the multi-bladed rotor 6 into a plurality of sub-volumes. In the illustrated position in Figure 1 of the rotor 6 with three wings two closed inside ^¬ lying measuring chambers 5 are formed. The liquid within the chambers can be exchanged by rotation of the rotor 6 with the outer liquid 3.

At the same time, the rotor blades delimit the chambers 5 to the outside. At the top of these chambers 5, an optical measuring window 7 is formed, through which a fiber-optic measurement can take place.

The rotor 6 is driven by a motor, preferably a stepping motor, and kept in a defined position for a measurement. As already mentioned, several vonein ^¬ other and encapsulated by the outer liquid 3 areas depending on the number of blades on the rotor 6 within the sample volume la thereby formed, which serve as measurement volumes or measuring ^¬ chambers. Each of these measuring chambers 5 can be assigned an optical measuring system. In the various chambers 5 can be at light-tight

Design of the wings of the rotor 6 simultaneously optical measurements are performed that do not affect each other. In the example of FIG. 1, supply channels 10, 11 are provided in the probe for carrying out the optical measurements, either in the case of the feed channel 10, an axis of rotation for the rotor 6 connected to a motor or, in the case of FIG Feed channels 11, the optical waveguides 12 and

Accommodate optics 8, 9 of an optical measuring system.

An optical measuring system each consists of a radiation source 15, a detector 14 and possibly a beam splitter 13. As the beam source 15 can, depending on

Measuring method, a narrow-band laser radiation source or a broadband light source can be used. The detector 14 may, depending on the application as

Spectrometer or monochromator or as a non-spectrally resolving detector, such as a photomultiplier or a photodiode be executed. The mentioned

Components of the measuring system are connected with optical fibers 12 with the optics 8, 9 within the measuring probe 1, in which then the measurements within the

Measuring chambers 5 take place. The beam splitter 13 can be omitted when using fiber bundles instead of simple fibers or optical waveguides 12, since then one or more fibers can only be used for the return of the backscattered light and the other fibers only for the supply of measuring light radiation.

A measurement with the device described is preferably divided into the following steps:

a) Immerse the probe in a calibration or

monitor fluid

b) activating rotations of the impeller to bring a representative volume of liquid into at least one measuring chamber,

c) Carrying out a calibration, recalibration or monitor measurement with the optical measuring method (s) used d) optionally rinsing the probe m a rinsing liquid and activation of the impeller rotation and / or the optionally provided piezo element for cleaning the chambers and the optical measuring window

e) Immerse the probe in the liquid to be measured inline

f) Activation of impeller rotation to bring representative volumes of liquid into at least one measuring chamber

g) stopping the impeller so that at least one measuring chamber forms a separate measuring volume with the liquid picked up by the vanes and decay convective flow components and come to rest

h) Performing optical measurements in one or more sealed measuring chambers

i) activation of the impeller to replace the

Liquid volumes against new representative

Liquid volumes of the surrounding liquid

j) optional activation unidirectional or

reversing vane wheel rotations to clean the measurement chambers and optical measurement windows of buildup.

In this way, a time series of measurement results can be obtained inline by a chemical

Reaction changing surrounding liquid can be obtained. Thus, a reaction sequence can be tracked and influenced by rules known per se. The apparatus and method thus provide in moving one or more fluids completed measuring chambers or compartments as measured ^¬ volumes for optical measuring systems are available in which decay convection of liquid to be measured and come to rest. You offer it the possibility of optical measuring systems at a location at which the probe is positioned to apply under the same conditions and Bedin ^¬ perform simultaneous measurements with different measuring methods. The measuring systems can without time delay, as for example by a conventionally required sampling and measurement after a sample preparation in a

separate measuring device is conditional, and can be used without elaborate preparations. Thus, with such a device, for example in the design of the probe as a backscatter DLS probe, during a technical process such as

chemical reaction, the particle size can be measured in an actively mixed liquid.

Reference sign list

1 measuring probe

la samples olumen

2 reactor vessel

3 Moving liquid

4 opening to the sample volume

5 Closed measuring chamber

6 rotor

7 Optical measuring window

8 optical element

9 Optical element

10 Feed channel for drive axle

11 Feed channel for optical fibers

12 optical fibers

13 beam splitter

14 detector

15 radiation source

Claims

claims

Apparatus for carrying out fiber optic

Measurements in moving liquids,

- having a measuring probe (1) with a probe body in which a sample volume (la)

is formed, which has at least one opening (4) for a replacement of a liquid sample,

- where on or in the sample volume (la) a

is arranged movable mechanical element through which at least a partial volume of the

Sample volume (la) can be completed mechanically to form a closed measuring chamber (5), and

- Wherein at the measuring chamber (5) an optical

Measuring window (7) for coupling and decoupling optical radiation into and out of the measuring chamber (5)

is trained.

Device according to claim 1,

characterized,

in that the measuring probe (1) has at least one fiber connection and optical elements (8, 9) for

Collimation or focusing of optical radiation from at least one can be coupled via the fiber connection optical fiber (12) through the optical measuring window (7) in the measuring chamber (5). Device according to claim 1,

characterized,

in that the measuring probe (1) is connected to at least one optical fiber (12) and optical elements (8, 9) for collimating or focusing optical radiation from the optical fiber (12) through the optical measuring window (7) into the

Measuring chambers (5).

Device according to one of claims 1 to 3, characterized

that the sample volume (la) is cylindrical

is formed and the mechanical element in the sample volume (la) rotatable rotation element

(6), by which the sample volume (la) is subdivided into at least two partial volumes which are completely separated from each other by the rotary element (6), wherein at least one of them has a partial volume

Position of the rotary element (6) at least one of the partial volumes the closed measuring chamber

(5) forms.

Device according to claim 4,

characterized,

in that the measuring probe (1) is connected to a drive for the rotary element (6), by means of which the rotary element (6) can be set in rotation. 6. Apparatus according to claim 4 or 5,

characterized,

that the rotation element (6) as an impeller is trained.

Device according to one of claims 4 to 6, characterized

in that the rotating element (6) has one or more scrapers, by means of which the optical measuring window (7) can be cleared of impurities during rotation of the rotary element (6).

Device according to one of claims 4 to 7, characterized

that the rotatable rotation element (6) the

Sample volume (la) divided into more than two completely separate sub-volumes, wherein in the at least one position of the

Rotational element (6) form a plurality of sub-volumes closed measuring chambers (5) on which an optical measuring window (7) is designed for coupling and decoupling optical radiation.

Method of conducting fiber optic

Measurements in moving liquids with a device according to one or more of

the preceding claims, in which

- The probe (1) in the examined

Liquid (3) is dipped,

the mechanical element is set in motion to convey a liquid sample into the at least one measuring chamber (5),

- the movement of the mechanical element

is then stopped in a position in which the measuring chamber (5) is closed, and

- After subsiding a liquid movement in the Measuring chamber (5) with one or more of the measuring probe (1) connected or to the measuring probe (1) coupled to fibers (12) a fiber optic measurement in the measuring chamber (5) is performed.

Method according to claim 9,

characterized,

that the mechanical element (6) is moved to the exchange of the liquid sample after carrying out the measurement and the last three steps of the method ^¬ are respectively repeated to carry out further fiber optical measurements.

Method according to claim 9 or 10,

characterized,

that as a fiber optic measurement, a dynamic light scattering measurement for determining a

Particle size of in the liquid sample

existing particles is carried out.

Method according to one of claims 9 to 11, characterized

that when forming a plurality of measuring chambers (5) several fiber optic measurements in parallel and without

mutual influence.