WO2017088887A1

WO2017088887A1 - A method of and a spectrometer for performing a nmr measurement on an electrically conducting fluid

Info

Publication number: WO2017088887A1
Application number: PCT/DK2016/050390
Authority: WO
Inventors: Michael Beyer; Ole Nørgaard JENSEN
Original assignee: Nanonord A/S
Priority date: 2015-11-25
Filing date: 2016-11-23
Publication date: 2017-06-01

Abstract

The invention comprises a NMR spectrometer comprising a hollow measuring zone and an inflow tube with an inflow tube length for feeding a fluid to be measured into the measuring zone, at least an innermost layer of said inflow tube is of an electrically insulating material, said NMR spectrometer further comprises an inflow valve arrangement configured for opening and closing said inflow tube, said NMR spectrometer preferably comprises an outflow tube with an outflow tube length for withdrawing a fluid from the measuring zone. The invention also comprises a method of performing a NMR measurement of an electrically conductive fluid.

Description

A METHOD OF AND A SPECTROMETER FOR PERFORMING A NMR MEASUREMENT ON AN ELECTRICALLY CONDUCTING FLUID

TECHNICAL FIELD

The invention relates to a NMR spectrometer suitable for performing a NMR measurement on an electrically conductive fluid. The invention also relates to a method of performing a NMR measurement on an electrically conductive fluid.

BACKGROUND ART

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a magnetic field absorb and re-emit electromagnetic radiation.

It is well known to perform NMR measurements on fluids and systems for NMR measurement of fluid have frequently been used in scientific assays and also downhole logging using nuclear magnetic resonance (NMR) within the oil and gas industry is well known.

US2011001474 describes a method and an apparatus for obtaining NMR signals from a flowing fluid, the apparatus includes a permanent magnet assembly for producing a magnetic field for NMR applications and

instrumentations, including flow metering. WO 2015070874 discloses a system for and a method of determining a least one quality parameter in an aqueous fluid. The method comprises subjecting at least a sample of the aqueous fluid to a cross-flow filtration in a cross-flow filter, separating the aqueous fluid into a permeate fraction and a retentate fraction, performing NMR reading on the retentate fraction using an NMR spectroscope, collecting NMR data from the NMR reading and correlating the collected NMR data to calibration data to determine the at least one quality parameter of the aqueous fluid. Performing NMR measurements of electrically conductive fluid in a flow through NMR spectrometer have generally been found to be difficult due to electrical noise.

DISCLOSURE OF INVENTION

An object of the invention is to provide an NMR spectrometer suitable for performing a NMR measurement on an electrically conductive fluid to obtain a relatively fast and accurate measurement with relatively low noise.

Another object of the invention is to provide a method of performing a NMR measurement on an electrically conductive fluid to obtain a relatively accurate result with a high signal to noise ratio.

These and other objects have been solved by the invention or embodiments thereof as defined in the claims and as described herein below.

It has been found that the invention or embodiments thereof have a number of additional advantages which will be clear to the skilled person from the following description.

It should be emphasized that the term "comprises/comprising" when used herein is to be interpreted as an open term, i.e. it should be taken to specify the presence of specifically stated feature(s), such as element(s), unit(s), integer(s), step(s) component(s) and combination(s) thereof, but does not preclude the presence or addition of one or more other stated features.

Reference made to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Further, the skilled person will understand that particular features, structures, or characteristics may be combined in any suitable manner within the scope of the invention as defined by the claims. The term "substantially" should herein be taken to mean that ordinary product variances and tolerances are comprised.

The phrases "NMR measurement" and "NMR reading" are used

interchangeably. Thanks to the invention NMR measurements of electrically conductive fluids can now be performed in a relatively simple way and with a high signal to noise result even when using a relatively low-field NMR spectrometer. The inventor(s) has thus provided a very effective and simple method of electrically shielding the NMR spectrometer to ensure low or no electrically induced noise due to external conductive fluid (outside the measuring zone). It is believed that the surprisingly effective electrical shielding provided by the method and the NMR spectrometer in embodiments of the invention is caused by electrically insulation of the portion of electrically conductive fluid in the measuring zone from external parts including the remaining of the electrically conductive fluid in the in- and/or outflow tubes.

The NMR spectrometer of the invention for performing NMR readings of electrically conductive fluids comprises a hollow measuring zone and an inflow tube with an inflow tube length for feeding a fluid to be measured into the measuring zone. In an embodiment at least an innermost layer of the inflow tube, which is adapted to be in contact with a fluid during filling into the measuring zone, is of an electrically insulating material. The NMR

spectrometer further comprises an inflow valve arrangement configured for opening (the valve arrangement is in open position) and closing (the valve arrangement is in closed position) the inflow tube. According to the invention it has been found that by ensuring that the fluid in the measuring zone is electrically insulated from the fluid in the inflow tube and optionally in the outflow tube a much more reliable measurement is obtained than without such insulation. In an embodiment the inflow tube also acts as outflow path from the measuring zone. However, generally it is desired that the NMR spectrometer comprises an outflow tube with an outflow tube length for withdrawing a fluid from the measuring zone. The lengths of the respective inflow tube and outflow tube are

advantageously sufficiently large to ensure a safe inflow and outflow of the fluid to be measured. In practice a length of 2 cm to 1 m or more is suitable, such as from about 20 -50 cm to allow a suitable space for valve

arrangements. The electrically insulating material may in principle be any kind of electrical insulation material, such as material which has an electrical conductance of less than about 100 mS/m, such as less than about 50 mS/m, such as less than about 5 mS/m, such as less than about 10 pS/rn, such as less than about 5 pS/m. Preferably the electrically insulating material is a polymer material.

Examples of suitable materials include rubber (nature rubber or synthetically rubber, e.g. silicone), polyolefin (PE), Polytetrafluorethylen (PTFE), polyamide (PA), Polyperfluoroalkoxyethylene (PFA), Polyoxymethylen acetal (POM) or mixtures or compounds comprising one or more of the before mentioned polymers.

In an embodiment the inflow tube is of an elastic material such that the inflow tube may be bent and/or compressed.

In an embodiment a section of the inflow tube is of an elastic material such that the inflow tube may be bent and/or compressed in that section while remaining rigid in its remaining part.

In an embodiment the inflow tube comprises an inner layer which in a section is of an elastic and expandable material to provide a valve function, such as a pressure controlled valve function as described further below. To ensure a long lifetime of the electrically insulating material it is

advantageously selected in dependence on the fluid for measurement in particular with due consideration to chemical compatibility.

To ensure a high electrical insulation the inflow valve arrangement preferably comprises a pinch valve arranged to pinch and unleash at least a part of the inflow tube for respectively closing and opening the inflow tube. The pinch valve is in particular beneficial where the fluid to be measured is an

inhomogeneous flued, such as a fluid comprising solid material, such as fibers, non- dissolved salts and other particles not dissolved or dissolvable in the fluid. It has been found that by using a pinch valve a very safe closure of the inflow tube may be obtained and further the pinch valve is simple to install and operate. Further the pinch valve may be returned to its open position such that the inflow tube is fully opened and advantageously free of narrow grooves or similar which may affect the flow or amass solids, such as particles from the fluid which may damage the valve.

In an embodiment the inflow tube is compressible and the pinch valve is arranged to pinch the inflow tube when in closed position. Advantageously the inflow tube material has an elasticity which is sufficiently high to ensure that the inflow tube fully reverts to its original open state by opening the pinch valve and unleashing the inflow tube.

In an embodiment the pinch valve is arranged outside the inflow tube and is arranged to pinch and unleash a section of the inflow tube. The section of the inflow tube which is pinched and unleashed has a length along the inflow tube which is also referred to as the valve length section. In an embodiment the pinch valve is at least partly integrated with the inflow tube. Preferably the inflow tube comprises a flexible inner membrane providing a part of the pinch valve. The flexible inner membrane is

advantageously elastic and preferably also expandable. In this embodiment is desired that the inflow tube, with the exception of the inner membrane providing the pinch valve function is rigid. This embodiment is very beneficial since the flow into and out of the measuring zone can be controlled with high accuracy. The term "rigid" is herein used to mean rigid under normal use of the NMR spectrometer at ambient temperature. In an embodiment the pinch valve in its closed position is closing off the inflow tube in a valve length section along the inflow tube length. It has been found that the valve length section advantageously should not be too short, since this may result in either a poor closure of the pinch valve or the pinch valve may form an undesired groove in the inflow tube which may affect the flow or amass solids, such as particles from the fluid such that the pinch may start to leak. The valve length section may be as long as practically desired. It has been found that the valve length section advantageously should have a length of at least about 0.5 cm, such as at least about 1 cm, such as at least about 2 cm, such as up to about 10 cm. Preferably the valve length section has a length of 1- 5 cm, more preferably about 3-4 cm.

The inflow valve arrangement may be operable by any means, such as a mechanical actuator e.g. electrically operated.

To ensure a fast and accurate operation of the inflow valve arrangement with low risk of generating electric noise to the NMR measurements, the inflow valve arrangement is advantageously pneumatically operable. Preferably the valve arrangement comprises a pinch valve which is closed off by pressurized gas, preferably such that upon release of pressurization the pinch valve is unleashed to open the inflow tube.

To further ensure a high electrical insulation the NMR spectrometer preferably comprises an inflow manifold arrangement upstream to the inflow valve arrangement for purging at least a section of the inflow tube, preferably when the valve arrangement is in its closed position. Advantageously the inflow manifold arrangement is adapted for purging the at least a section of the inflow tube by liquid, such as by an aqueous liquid e.g. water.

Thereby the fluid to be measured may flow via the inflow tube into the measuring zone, the inflow valve arrangement may be switched to closed position to close the inflow tube, the inflow tube upstream to the inflow valve arrangement is purged and thereafter the NMR reading is performed substantially without any electrically induced noise due to electrically conductive fluid in the inflow tube. The electrically conductive fluid is advantageously withdrawn via an outflow tube.

As mentioned the NMR spectrometer preferably comprises an outflow tube for withdrawing the portion of electrically conductive fluid from the measuring zone after the NMR readings have been terminated for that portion of fluid. The outflow tube comprises at least an innermost layer, which is adapted to be in contact with a fluid during withdrawal from the measuring zone, and which is of an electrically insulating material, the NMR spectrometer further comprises an outflow valve arrangement configured for opening and closing the outflow tube. The outflow tube may preferably be as described above for the inflow tube. It should be noted that the inflow tube and the outflow tube need not be identical although it is practical to have substantially identical inflow tube and outflow tube.

The outflow valve arrangement may be as described above for the inflow valve arrangement. The outflow valve arrangement and the inflow valve arrangement are advantageously coordinated to be opened respectively closed simultaneously.

In an embodiment the pinch valve of the inflow valve arrangement and the pinch valve of the outflow valve arrangement are pneumatically operable by a common pneumatic system. Preferably the pinch valve of the inflow valve arrangement and the pinch valve of the outflow valve arrangement are operated to their respective closed positions by pressurized gas from a common pneumatic source, preferably such that upon release of

pressurization the pinch valves are unleashed to open the inflow tube and the outflow tube.

The outflow manifold arrangement downstream to the outflow valve arrangement is preferably as described for the inflow manifold arrangement upstream to the inflow valve arrangement. The outflow manifold arrangement and the inflow manifold arrangement are preferably coordinated to perform the purging of the section of the outflow tube and the section of the inflow tube in a coordinated way, preferably simultaneously. The outflow manifold arrangement and the inflow manifold arrangement are advantageously in the form of a common inflow/outflow manifold arrangement. Thereby the fluid to be measured may flow via the inflow tube into the measuring zone, the inflow valve arrangement may be switched to its closed position and simultaneously the outflow valve arrangement is switched to its closed position, the inflow tube upstream to the inflow valve arrangement and the outflow tube downstream to the outflow valve arrangement are purged via the common inflow/outflow manifold arrangement and thereafter the NMR reading is performed substantially without any electrically induced noise due to electrically conductive fluid in the inflow tube. Finally the inflow valve arrangement and the outflow valve arrangement are switched to its open position, the portion of fluid in the measuring zone is withdrawn via the outflow tube and a fresh portion of fluid is fed to the measuring zone via the inflow tube. The NMR spectrometer may advantageously comprise a backflush arrangement for rinsing the measuring zone and preferably the inflow tube and outflow tube before feeding a fresh portion of fluid to be measured into the measuring zone. In an embodiment the measuring zone comprises an electrically insulating annular confinement inner wall. It has been found that for measuring highly electrically conductive fluids electrically insulating the measuring zone may result in even further reduction of electric noise. The inner wall of the measuring zone is advantageously rigid to ensure an accurate volume of sample within the measuring zone during the NMR readings.

Advantageously the annular confinement inner wall preferably comprises a measuring zone tube, which advantageous is rigid. In a preferred embodiment the inflow tube, the measuring zone tube and the outflow tube form respective sections of a common NMR tube.

The common NMR tube may advantageous be an exchangeable tube, such that it may be replaced with a fresh common NMR tube after a certain time of use - e.g. because of wear - or the NMR spectrometer may comprise a set of different common NMR tubes suitable for use for performing NMR

measurements on different types of electrically conductive fluids.

By providing the inflow tube, the measuring zone tube and the outflow tube in the form of the common NMR tube a highly desired flow through setup may be obtained which is very simple to operate including filling and emptying the measuring zone.

A NMR spectrometer with such common NMR tube has been found to be highly advantageous for use for performing NMR measurements of

suspensions comprises solids, e.g. particles, such as slurries with high concentrations of solids, for example waste water or manure. The suspension is simple to feed into and withdraw from the measuring zone and the common NMR tube is simple to clean simply by flushing by liquid e.g. water.

Advantageously the common NMR tube provides a flow through tube suitable for performing NMR readings on a sample in a semi flowing condition, comprising holding a sample portion quiescent in the measuring zone during NMR measurement.

In an embodiment the common NMR tube has an inner surface which, at least when the valve arrangements are in their open positions, is substantially free off grooves, the inner surface is preferably substantially smooth, preferably having an Arithmetical Mean Roughness (Ra value) of 0.5 pm or less, such as about 0.2 pm or less, such as about 0.1 pm or less, such as about 50 nm or less.

The Ra-value may be measured in accordance with the ISO 4287, DIN 4762 and/or DIN 4768 standards, with a roughness cut-off wavelength, L_c of 2.5 mm.

In an embodiment the NMR spectrometer comprises at least one magnet for generating a magnetic field at the measuring zone and a RF transmit and/or receive coil system arranged to transmit and/or receive RF signals to/from a fluid in the measuring zone.

Preferably the one or more magnets arranged to generate the magnetic field are relatively small magnets with low magnetic force. By using such relatively small/low force magnets the NMR spectrometer becomes much cheaper and further the required size of the NMR spectrometer is highly reduced which makes it much simpler to use e.g. as a transportable NMR spectrometer.

Preferably the NMR spectrometer is a low-field NMR spectrometer comprises one or more magnets arranged to generate a maximal magnetic field of up to about 2.5 Tesla, preferably of from 0.1 to 2 Tesla.

Such low-field NMR spectrometer is less costly compared to NMR

spectrometer with magnets arranged to generate higher maximal magnetic fields. Due to the construction of the NMR spectrometer of embodiments of the claimed invention it has been found that such a low-field NMR

spectrometer (i.e. maximal magnetic fields of up to about 2.5 Tesla) and thereby relatively low cost NMR spectrometer is suitable for use for

performing NMR measurements on electrically conducting fluid samples.

In an embodiment the NMR spectrometer comprises a permanent magnet, such as a neodymium magnet. Since permanent magnets are generally not costly, this solution provides a low cost solution which for many applications may provide a sufficiently low noise and highly reliable result.

In an embodiment the NMR spectrometer comprises an electromagnet, such as a solenoid magnet. In an embodiment the NMR spectrometer comprises a permanent magnet in combination with an electromagnet which

advantageously is constructed for providing an adjustable and/or a pulsed magnetic field.

Any NMR spectrometer has a spectrometer frequency range which gives the maximal operation range of the spectrometer.

Advantageously the NMR spectrometer has a spectrometer frequency range of up to about 85 MHz, such as up to about 50 MHz, such as from about 1- 200 MHz.

In an embodiment the NMR spectrometer has a spectrometer frequency range of about 7-10 MHz. A spectrometer frequency range of 10 MHz results in a domain spectra with a frequency width per ppm of about 70 Hz/ppm. In an embodiment the NMR spectrometer comprises at least one pump (e.g. a piston pump) operatively connected to at least one of the inflow and/or outflow tubes for feeding and/or withdrawing fluid to/from the measuring zone.

In an embodiment the NMR spectrometer comprises a water inflow

arrangement, such as a water backflow arrangement. Such a water backflow arrangement is preferably applied for rinsing the measuring zone after withdrawing a portion of electrically conductive fluid from the measuring zone. The water backflow arrangement and in- and outflow arrangements are integrated to use a common water supply for the backflow rinsing and the purging.

In an embodiment the NMR spectrometer comprises a computer system configured for operating the NMR spectrometer, the computer system preferably being configured for operating the NMR spectrometer to perform a method as described below.

In an embodiment the NMR spectrometer is configured for being calibrated by calibration liquid comprising known quantities of 1H isotopes and/or 170 isotopes. The computer system is programmed to pump the calibration water into the measuring zone and perform at least one 1H NMR reading and/or at least one 170 NMR reading obtaining at least one spectra and correlating the at least one spectra to the known quantities of 1H isotopes and/or 170 isotopes.

Surprisingly it has been found that a very accurate calibration may be obtained by using calibration water. The term "calibration water" is used to designate water with known quantities of 1H isotopes and 170 isotopes. The water may comprise other elements, provided that they are not interfering with 1H NMR reading or 170 NMR reading Surprisingly it has been found that calibration water is ideal for calibrating the correct frequencies of all isotopes of interest such as isotopes of Na, Al, Li, C, N, P,K, F, CI and/or Br, and for calibrating system response, i.e. Signal intensity as function of amount of given analyte.

The system may comprise one, two or more computers, one, two or more spectrometers and/or one, two or more calibration maps. The system may preferably be in data communication with the internet e.g. for communication with other similar systems, for sending and/or receiving data. The system may preferably comprise at least one display and/or an operating keyboard as well as any other digital equipment usually connected to digital systems, e.g. printers. The invention also comprises a method of performing a NMR measurement of an electrically conductive fluid using an NMR spectrometer.

The method of performing a NMR measurement of an electrically conductive fluid using an NMR spectrometer as described above comprises · feeding a portion of the electrically conductive fluid into the measuring zone;

• closing the inflow tube by the inflow valve arrangement,

• performing at least one NMR reading on the portion of electrically

conductive fluid comprising reading at least one NMR readable isotope, and

• withdrawing the portion of electrically conductive fluid from the

measuring zone.

The method may advantageously be performed as described in any one of WO2013/087077, WO2013/087076, WO2015/070872 and/or WO2015/070874 with the difference that it is performed using the above described NMR spectrometer and comprises the above listed steps.

General information of performing NMR measurements may for example be found in WO2013/087077, WO2013/087076, WO2015/070872 and/or

WO2015/070874. As described the withdrawing of the portion of electrically conductive fluid from the measuring zone may be performed via the inflow tube or preferably via the outflow tube.

The method advantageously further comprises purging at least a length section of the inflow tube upstream to the inflow valve arrangement. The purging is preferably performed via the inflow manifold arrangement. The inflow manifold arrangement comprises a manifold to the inflow tube which is optionally crossing the inflow tube. Preferably the purging is performed after closing the inflow tube by the inflow valve arrangement but before performing the at least one NMR reading. Thereby it is ensured that the fluid used for purging (purging fluid) is not intermixed with the portion of electrically conductive fluid in the measuring zone.

The purging is advantageously performed to remove all electrically conducting substances (the remaining sample material) in the inflow tube and the outflow tube or at least a length thereof of, such as at least a length of at least about 1 cm, such as at least about 2 cm, such as at least about 5 cm of each of the inflow tube and the outflow tube.

The purging fluid may in principle be any type of fluid and preferably liquid with a relatively low electrical conductivity, such as with an electrical conductivity which is lower than the electrical conductivity of the electrically conductive fluid under measurement. Preferably the purging fluid has an electrical conductivity up to about 50 mS/m, such as up to about 5 mS/m, such as up to about 10 pS/m.

Examples of suitable purging fluids are for example pressurized gas, oil or water, such as tap water or desalinated water. For a highly effective purging liquid, such as water is preferred.

In an embodiment the purging fluid is ultra-pure water (5.5pS/m).

The purging advantageously comprises flushing the inner surfaces of the manifold and/or the length section of the inflow tube clean of the electrically conductive fluid.

Dry air may be applied to dry the manifold and/or the length section of the inflow tube.

Advantageously the method comprises

• feeding the portion of the electrically conductive fluid into the

measuring zone;

• closing the inflow tube by the inflow valve arrangement and closing the outflow tube by the outflow tube arrangement, • purging (preferably using a purging liquid e.g. water) at least a length section of the inflow tube upstream to the inflow valve arrangement and at least a length section of the outflow tube downstream to the outflow valve arrangement

· performing the at least one NMR reading on the portion of electrically conductive fluid,

• opening the outflow tube by the outflow tube arrangement, and

• withdrawing the portion of electrically conductive fluid from the

measuring zone via the outflow tube. The purging of the outflow tube is preferably performed as described for the inflow tube.

In an embodiment the electrically conductive fluid to be measured is pumped via the inflow tube into the measuring zone, the inflow valve arrangement is be switched to its closed position and simultaneously the outflow valve arrangement is switched to its closed position, the inflow tube upstream to the inflow valve arrangement and the outflow tube downstream to the outflow valve arrangement are purged via the common inflow/outflow manifold arrangement and thereafter the NMR reading is performed substantially without any electrically induced noise due to electrically conductive fluid in the inflow tube. Finally the inflow valve arrangement and the outflow valve arrangement are switched to its open position, the portion of fluid in the measuring zone is withdrawn via the outflow tube and a fresh portion of fluid is fed to the measuring zone via the inflow tube. The method advantageously comprises flushing the measuring zone and preferably the inflow tube and outflow tube before feeding a fresh portion of fluid to be measured into the measuring zone, e.g. by back-flushing a rinsing fluid which e.g. is as described for the purging fluid.

In an embodiment the method comprises performing a NMR measurement on two or more consecutive portions of the electrically conductive fluid, the method comprises • feeding a first portion of the electrically conductive fluid into the measuring zone via the inflow tube;

• closing the inflow tube by the inflow valve arrangement and closing the outflow tube by the outflow tube arrangement,

· purging at least a length section of the inflow tube upstream to the inflow valve arrangement and at least a length section of the outflow tube downstream to the outflow valve arrangement

• performing the at least one NMR reading on the first portion of

electrically conductive fluid,

· opening the outflow tube by the outflow tube arrangement, and

• feeding a second portion of the electrically conductive fluid into the measuring zone via the inflow tube while simultaneously withdrawing the first portion of electrically conductive fluid from the measuring zone via the outflow tube, and repeating the measuring sequence. According to the invention it has been found that any kind of electrically conductive fluid may be measured using the NMR spectrometer and the described method. In an embodiment the electrically conductive fluid is an aqueous solution, dispersion or suspension, such as a waste water sludge, manure, an ionic solution or a suspension of solid matter, such as particles and/or fibers.

The method of the invention has been found to be in particular beneficial for NMR measurement of electrically conductive fluids comprising suspended solids, the suspended solids may be any kind of solids, such as particles, fibers, agglomerates, gelled particles and any other. Examples of such fluids include waste water sludge, biomass, fermented fluid and manure with varying amount of solids.

In a preferred embodiment the inflow tube, the measuring zone tube as described above and the outflow tube form respective sections of a common NMR tube forming a flow through tube and the method comprises performing NMR readings on a sample in a semi flowing condition, comprising holding a sample portion quiescent in the measuring zone during NMR reading.

In another aspect it has been found that using calibration liquid, such as calibration water s explained above comprising known quantities of 1H isotopes and/or 170 isotopes for calibrating a NMR spectrometer, such as the NMR spectrometer described above, results in a surprisingly valid calibration as further described above.

The invention therefore also relates to a method of calibrating a NMR spectrometer comprising calibrating the NMR spectrometer by calibration water comprising known quantities of 1H isotopes and 170 isotopes, the method comprises pumping the calibration water into the measuring zone and performing at least one 1H NMR reading and at least one 170 NMR reading obtaining at least one spectra and correlating the at least one spectra to the known quantities of 1H isotopes and 170 isotopes. All features of the invention including ranges and preferred ranges can be combined in various ways within the scope of the invention, unless there are specific reasons not to combine such features.

BRIEF DESCRIPTION OF EXAMPLES AND DRAWINGS

The invention is being illustrated further below in connection with reference to the figures.

The figures are schematic and are not drawn to scale and may be simplified for clarity. Throughout, the same reference numerals are used for identical or corresponding parts.

Figure 1 is a schematic drawing of an embodiment of a NMR spectrometer of the invention.

Figure 2 is a schematic drawing of another embodiment of a NMR

spectrometer of the invention. Figure 3 is a schematic drawing of yet another embodiment of a NMR spectrometer of the invention.

Figure 4 is a schematic drawing of a variation of the embodiment shown in figure 3. Figure 1 shows a NMR spectrometer comprising a measuring zone 1 and an inflow tube 2 with an inflow tube length for feeding a fluid to be measured into the measuring zone 1. A not shown magnet is arranged in a NMR base 3 for generating a magnetic field at the measuring zone 1. The NMR base also comprises a not shown RF transmit and/or receive coil system arranged to transmit and/or receive RF signals to/from a fluid in the measuring zone 1. The NMR spectrometer also comprises an outflow tube 4 with an outflow tube length for withdrawing a fluid from the measuring zone 1. At least an innermost layer of the inflow tube 2 and of the outflow tube 4 is of an electrically insulating material. In the shown embodiment the hollow measuring zone 1 comprises an electrically insulating annular confinement inner wall 5 provided by a measuring zone tube 5 and the inflow tube 2, the measuring zone tube 5 and the outflow tube 4 form respective sections of a common NMR tube 2, 5, 4 which is of an electrically insulating material.

The common NMR tube 2, 5, 4 thereby provides a flow through tube suitable for performing NMR readings on a sample in a semi flowing condition, comprising holding a portion of electrically conductive fluid quiescent in the measuring zone during NMR measurement.

As indicated with the dotted line a further electrical screen is advantageously arranged to electrically shield the NMR base 3 comprising the magnet and the pinch valve arrangements 6, 7.

The NMR spectrometer further comprises an inflow valve arrangement 6 configured for opening and closing said inflow tube 2 and an outflow valve arrangement 7 configured for opening and closing the outflow tube 4. The NMR spectrometer also comprises a not shown pump operatively connected to at least one of the inflow tube 2 and the outflow tube 4 for feeding and withdrawing fluid to and from the measuring zone 1.

The valve arrangements 6,7 each have an open position and a closed position and the inflow valve arrangement 6 and the outflow valve arrangement 7 are advantageously correlated to be in an open respective closed position simultaneously.

In use the inflow valve arrangement 6 and the outflow valve arrangement 7 are in their open position and the pump is turned on for feeding a portion of electrically conductive fluid via the inflow tube 2 to the measuring zone 1 and thereafter the pump is turned off. The inflow valve arrangement 6 and the outflow valve arrangement 7 are switched to their closed position and the NMR readings are started. Preferably a plurality of NMR readings is performed. Thereafter the inflow valve arrangement 6 and the outflow valve arrangement 7 are switched to their open position and the pump is turned on to withdraw the portion of electrically conductive fluid in the measuring zone 1 and to feed in a fresh portion of electrically conductive fluid.

Figure 2 shows a NMR spectrometer comprising a measuring zone 1 and an inflow tube 12 with an inflow tube length for feeding a fluid to be measured into the measuring zone 11. The arrow I indicates the inflow direction of the electrically conductive fluid. A not shown magnet is arranged in a NMR base 13 for generating a magnetic field at the measuring zone 11. The NMR base also comprises a not shown RF transmit and/or receive coil system arranged to transmit and/or receive RF signals to/from a fluid in the measuring zone 11. The NMR spectrometer also comprises an outflow tube 14 with an outflow tube length for withdrawing a fluid from the measuring zone 11. The arrow 0 indicates the outflow direction.

At least an innermost layer of the inflow tube 11 and of the outflow tube 14 is of an electrically insulating material. The hollow measuring zone 11 comprises an electrically insulating annular confinement inner wall 15 provided by a measuring zone tube 15 and the inflow tube 12, the measuring zone tube 15 and the outflow tube 14 form respective sections of a common NMR tube 12, 15, 14 which is of an electrically insulating material. The common NMR tube 12, 15, 14 is advantageously rigid except for an inner expandable membrane which forms part of the valve arrangements as described below.

The NMR spectrometer further comprises an inflow valve arrangement 16 configured for opening and closing said inflow tube 12 and an outflow valve arrangement 17 configured for opening and closing the outflow tube 14.

The inflow valve arrangement 16 comprises a pinch valve 16 arranged to pinch the inflow tube 12 to be in closed position as indicated with ref. 16a. The pinch valve 16 in closed position is closing off the inflow tube 12 in a valve length section along the inflow tube length.

The outflow valve arrangement 17 is similar to the inflow valve arrangement 16 and comprises a pinch valve 17 arranged to pinch the outflow tube 14 to be in closed position. The pinch valve 17 in its closed position is closing off the outflow tube 14 in a valve length section 17a along the outflow tube length. As indicated with the references 16a and 17a the inner expandable membrane forms part of the pinch valves 16, 17.

The inflow valve arrangement 16 and the outflow valve arrangement 17 are pneumatically operable and each comprises a pressure box 16b, 17b connected to a not shown pressure control arrangement via pipes 18. Upon pressurization of the pressure boxes 16b, 17b the pinch valves 16, 17 are switched to their closed position. Upon release of pressurization the pinch valves are unleashed to open the inflow tube and the outflow tube. As it can be seen the common NMR tube 12, 15, 14 has an inner surface which is smooth and substantially free of grooves.

The NMR spectrometer also comprises an inflow manifold arrangement 19a upstream to the inflow valve arrangement for purging at least a section of the inflow tube 12, preferably when the valve arrangement 16 is in its closed position as well as a corresponding outflow manifold arrangement 19b downstream to said outflow valve arrangement 17 for purging at least a section of the outflow tube 17, preferably when the valve arrangement is in its closed position. Advantageously the inflow and outflow manifold

arrangements are arranged to ensure an efficient purging of the inflow tube and the outflow tube respectively adjacent to the respective pinch valves 16, 17.

The inflow manifold arrangement 19a comprises a manifold pipe 19c crossing the inflow tube 12 and on/off valves 19d arranged on either side of the inflow tube 12. The ref. P indicates the flow direction of the purging fluid which is fed from a not shown purging fluid source. The outflow manifold arrangement 19b is as described for the inflow manifold arrangement 19a.

The NMR spectrometer also comprises at least one and preferably at least two not shown pumps operatively connected to at least one of the inflow tube 12 and the outflow tube 14 for feeding and withdrawing fluid to and from the measuring zone 11 and for purging the inflow tube and the outflow tube.

In use the on/off valves 19d are in their closed position, the inflow valve arrangement 16 and the outflow valve arrangement 17 are in their open position and the pump is turned on for feeding a portion of electrically conductive fluid via the inflow tube 12 to the measuring zone 11 and thereafter the pump is turned off. The inflow valve arrangement 16 and the outflow valve arrangement 17 are switched to their closed position and the on/off valves 19d are switched to their open position and a purging fluid is pumped through the manifold pipes 19c crossing respectively the inflow tube 12 and the outflow tube 14. The purging is advantageously reaching the expanded membrane 16a, 17a of the pinch valves 16,17. After purging with purging fluid, dry air may be sent through the manifold pipes 19c to dry the manifold pipes 19c and at least the immediate adjacent sections of the inflow tube and the outflow tube and the on/off valves 19d are switched to their closed position. After this the NMR readings are started. After termination of the NMR readings the inflow valve arrangement 16 and the outflow valve arrangement 17 are switched to their open position and the pump is turned on to withdraw the portion of electrically conductive fluid in the measuring zone 11 and to feed in a fresh portion of electrically conductive fluid and the steps are repeated.

Figure 3 show a NMR spectrometer comprising a not shown measuring zone and an inflow tube 22 for feeding a fluid to be measured into the measuring zone. The arrow I indicates the inflow direction of the electrically conductive fluid. A not shown magnet is arranged in a NMR base 23 for generating a magnetic field at the measuring zone. The NMR base 23 also comprises a not shown RF transmit and/or receive coil system arranged to transmit and/or receive RF signals to/from a fluid in the measuring zone. The NMR

spectrometer also comprises an outflow tube 24 for withdrawing a fluid from the measuring zone. The arrow 0 indicates the outflow direction of the electrically conductive fluid.

At least an innermost layer of the inflow tube 22 and of the outflow tube 24 is as described above.

The NMR spectrometer further comprises a not shown inflow valve

arrangement configured for opening and closing said inflow tube 22 and a not shown outflow valve arrangement configured for opening and closing the outflow tube 24.

The NMR spectrometer also comprises an inflow manifold arrangement 29a upstream to the inflow valve arrangement for purging at least a section of the inflow tube 22, preferably when the valve arrangement 26 is in its closed position as well as a corresponding outflow manifold arrangement 29b downstream to said outflow valve arrangement for purging at least a section of the outflow tube 24, preferably when the valve arrangement is in its closed position. The inflow manifold arrangement 29a and the outflow manifold arrangement 29b comprise a manifold pipe arrangement 28 with a purging valve 28a. The NMR spectrometer also comprises a piston pump arrangement 25 and a water supply W. A connection pipe section 30a connects the outflow tube 24 to the piston pump arrangement 25 and a water supply W. The connection pipe section 30a may advantageous have a relatively small cross-sectional area to ensure that the flow within the connection pipe section 30a has a low turbulence or preferably is laminar to avoid undesired mixture of sample and purging water in the connection pipe section 30a. In the embodiment shown in figure 4 the connection pipe section 30a has been replaced by a folded connection pipe section 30b. The folded connection pipe section 30b ensures that the sample, which may comprise corrosive components, does not enter the piston pump arrangement 25 and thereby the risk of corroding the piston pump arrangement 25 is reduced.

Simultaneously the NMR spectrometer may be kept very compact, which is beneficial in particular for simple transport of NMR spectrometer. The folded connection pipe section 30b also may ensure a mechanical protection thereof.

The folded connection pipe section 30b may be folded with any kind of folds, preferably without sharp edges. The folded connection pipe section 30b may e.g. be meander folded or preferably coiled with touching or non-touching windings.

The NMR spectrometer may additionally comprise a not shown temperature regulator for regulating the temperature of the sample liquid in the

connection pipe section 30b. The temperature regulator may advantageously be arranged in contact with the folded connection pipe section 30b.

The piston pump arrangement has at least three positions, position a) where it is pumping electrically conductive fluid in and/or out of the measuring zone in the NMR base 23, position b) where it is pumping water in the opposite direction and position c) where it is shut down. The skilled person will know to provide other pump arrangements. For example the pump may not have position b) instead when the pump is shut down the remaining water pressure is used to purge the system.

In use the purging valve 28a is in its closed position, the inflow valve arrangement and the outflow valve arrangement are in their open position and the piston pump arrangement 25 is turned on in position a) for feeding a portion of electrically conductive fluid via the inflow tube 22 to the measuring zone and thereafter the piston pump arrangement 25 is turned off to position c). The inflow valve arrangement and the outflow valve arrangement are switched to their closed position and the purging valve 28a is switched to its open position. The piston pump arrangement 25 is now switched to position b) to pump water (purging liquid) through the manifold pipe arrangement 28 to purge a section of respectively the inflow tube 22 and the outflow tube 24. The water is pumped out as indicated with ref WO. A not shown valve arrangement may be positioned to ensure that the out-pumped water is not mixed with the reservoir of electrically conductive fluid which is to be pumped to the measuring zone later on. After purging with water the pump

arrangement 25 is turned off to position c) and the purging valve 28a is in its closed position. After this the NMR readings are started. After termination of the NMR readings the inflow valve arrangement 26 and the outflow valve arrangement 17 are switched to their open position and the pump is turned on to withdraw the portion of electrically conductive fluid in the measuring zone. Thereafter the piston pump arrangement 25 is now switched to position b) to pump water in a water backflow arrangement through the outflow tube 24, the measuring zone and the inflow tube 22 to rinse the tubes and the water is pumped out as indicated with ref WO. Thereafter the steps may be repeated.

Claims

PATENT CLAIMS

1. A NMR spectrometer comprising a hollow measuring zone and an inflow tube with an inflow tube length for feeding a fluid to be measured into the measuring zone, at least an innermost layer of said inflow tube is of an electrically insulating material, said NMR spectrometer further comprises an inflow valve arrangement configured for opening and closing said inflow tube, said NMR spectrometer preferably comprises an outflow tube with an outflow tube length for withdrawing a fluid from the measuring zone.

2. The NMR spectrometer of claim 1, wherein the NMR spectrometer comprises an inflow manifold arrangement upstream to said inflow valve arrangement for purging at least a section of the inflow tube, preferably when the valve arrangement is in its closed position.

3. The NMR spectrometer of claim 1 or claim 2, wherein the inflow valve arrangement comprises a pinch valve.

4. The NMR spectrometer of claim 3, wherein the inflow tube is compressible and the pinch valve is arranged to pinch the inflow tube when it is in its closed position.

5. The NMR spectrometer of any one of claims 3 and 4, wherein the pinch valve is at least partly integrated with the inflow tube.

6. The NMR spectrometer of any one of claims 3 -5, wherein the inflow tube comprises a flexible inner membrane providing a part of the pinch valve, preferably the flexible inner membrane is expandable, more preferably the remaining inflow tube is substantially rigid.

7. The NMR spectrometer of any one of claims 3 -6, wherein the pinch valve in its closed position is closing off the inflow tube in a valve length section along the inflow tube length, said valve length section having a length of at least about 1 cm, such as at least about 2 cm, such as up to about 10 cm, preferably about 3-4 cm.

8. The NMR spectrometer of any one of the preceding claims, wherein the inflow valve arrangement is pneumatically operable, preferably the valve arrangement comprises a pinch valve which is closed off by pressurized gas, preferably such that upon release of pressurization the pinch valve is unleashed to open the inflow tube.

9. The NMR spectrometer of any one of the preceding claims, wherein the inflow tube is of electrically insulating material, preferably a polymer material, such as rubber, polyolefin (PE), Polytetrafluorethylen (PTFE), polyamide (PA), Polyperfluoroalkoxyethylene (PFA), Polyoxymethylen acetal (POM) or mixtures or compounds comprising one or more of the before mentioned polymers.

10. The NMR spectrometer of any one of the preceding claims, wherein the NMR spectrometer comprises said outflow tube, said outflow tube comprises at least an innermost layer, and which is of an electrically insulating material, said NMR spectrometer further comprises an outflow valve arrangement configured for opening and closing said outflow tube.

11. The NMR spectrometer of any one of the preceding claims, wherein the outflow tube is of electrically insulating material, preferably a polymer material, such as rubber, polyolefin (PE), Polytetrafluorethylen (PTFE), polyamide (PA), Polyperfluoroalkoxyethylene (PFA), Polyoxymethylen acetal (POM) or mixtures or compounds comprising one or more of the before mentioned polymers.

12. The NMR spectrometer of claim 10 or claim 11, wherein the outflow valve arrangement comprises a pinch valve.

13. The NMR spectrometer of claim 12, wherein the outflow tube is compressible and the pinch valve is arranged to pinch the outflow tube when it is in its closed position.

14. The NMR spectrometer of any one of claims 12 and 13, wherein the pinch valve is at least partly integrated with the outflow tube.

15. The NMR spectrometer of any one of claims 12 -14, wherein the outflow tube comprises a flexible inner membrane providing a part of the pinch valve, preferably the flexible inner membrane is expandable, more preferably the remaining outflow tube is substantially rigid .

16. The NMR spectrometer of any one of claims 11 -15, wherein the pinch valve in its closed position is closing off the outflow tube in a valve length section along the outflow tube length, said valve length section having a length of at least about 1 cm, such as at least about 2 cm, such as up to about 10 cm, preferably about 3-4 cm.

17. The NMR spectrometer of any one of the preceding claims 10-16, wherein the outflow valve arrangement is pneumatically operable, preferably the valve arrangement comprises a pinch valve which is closed off by pressurized gas, preferably such that upon release of pressurization the pinch valve is unleashed to open the outflow tube.

18. The NMR spectrometer of any one of the preceding claims 10-17, wherein the NMR spectrometer comprises an outflow manifold arrangement downstream to said outflow valve arrangement for purging at least a section of the outflow tube, preferably when the valve arrangement is in its closed position.

19. The NMR spectrometer of any one of the preceding claims, wherein said measuring zone comprises an electrically insulating annular confinement inner wall, said annular confinement inner wall preferably comprises a measuring zone tube, said measuring zone tube preferably being substantially rigid.

20. The NMR spectrometer of claim 19, wherein said inflow tube, said measuring zone tube and said outflow tube form respective sections of a common NMR tube.

21. The NMR spectrometer of claim 20, wherein said common NMR tube provides a flow through tube suitable for performing NMR readings on an electrically conductive fluid in a semi flowing condition, comprising holding a portion of electrically conductive fluid quiescent in the measuring zone during NMR measurement.

22. The NMR spectrometer of claim 20 or claim 21, wherein said common NMR tube has an inner surface which, at least when the valve arrangements are in their open positions, is substantially free of grooves, said inner surface is preferably substantially smooth, preferably having an Arithmetical Mean Roughness (Ra value) of 0.5 pm or less, such as about 0.2 pm or less, such as about 0.1 pm or less, such as about 50 nm or less.

23. The NMR spectrometer of any one of the preceding claims, wherein said NMR spectrometer comprises a magnet for generating a magnetic field at said measuring zone and a RF transmit and/or receive coil system arranged to transmit and/or receive RF signals to/from a fluid in said measuring zone.

24. The NMR spectrometer of any one of the preceding claims, wherein said NMR spectrometer comprises at least one pump arrangement operatively connected to at least one of said inflow and/or outflow tubes for feeding and/or withdrawing fluid to/from said measuring zone, said pump

arrangement preferably being a piston pump.

25. The NMR spectrometer of claim 24, wherein said NMR spectrometer comprises a connection pipe section connecting said inflow and/or outflow tubes outflow tube to the piston pump arrangement.

26. The NMR spectrometer of claim 25, wherein said connection pipe section connecting said inflow and/or outflow tubes outflow tube to the piston pump arrangement is a folded connection pipe section, preferably said connection pipe section is meander folded or coiled.

27. The NMR spectrometer of any one of the preceding claims, wherein said NMR spectrometer comprises a temperature regulator for tempering the liquid sample, said temperature regulator preferably being arranged in contact with said connection pipe section connecting said inflow and/or outflow tubes outflow tube to the piston pump arrangement.

28. The NMR spectrometer of any one of the preceding claims, wherein said NMR spectrometer comprises a water inflow arrangement, such as a water backflow arrangement.

29. The NMR spectrometer of any one of the preceding claims, wherein said NMR spectrometer comprises a computer system configured for operating said NMR spectrometer, said computer system preferably being configured for operating said NMR spectrometer to perform a method according to any one of the following claims.

30. The NMR spectrometer of claim 29, wherein said NMR spectrometer is configured for being calibrated by calibration liquid comprising known quantities of 1H isotopes and/or 170 isotopes, said computer system being programmed to pump the calibration water into the measuring zone and perform at least one 1H NMR reading and at least one 170 NMR reading obtaining at least one spectra and correlating the at least one spectra to the known quantities of 1H isotopes and/or 170 isotopes, said calibration liquid preferably being calibration water.

31. A method of performing a NMR measurement of an electrically conductive fluid using an NMR spectrometer according to any one of the preceding claims, said method comprising

• feeding a portion of said electrically conductive fluid into said

measuring zone;

• closing said inflow tube by said inflow valve arrangement,

· performing at least one NMR reading on said portion of electrically conductive fluid comprising reading at least one NMR readable isotope, and

• withdrawing said portion of electrically conductive fluid from said

measuring zone.

32. The method of claim 31, wherein said withdrawing of said portion of electrically conductive fluid from said measuring zone is performed via said inflow tube or preferably via said outflow tube.

33. The method of claim 31 or claim 32, further comprising purging at least a section of said inflow tube upstream to said inflow valve arrangement, said purging is preferably performed via said inflow manifold arrangement, more preferably said purging is performed after closing said inflow tube by said inflow valve arrangement but before performing said at least one NMR reading.

34. The method of claim 333, wherein said purging is performed using a purging fluid having an electrical conductivity which is lower than the electrical conductivity of the electrically conductive fluid under measurement, preferably said purging fluid has an electrical conductivity up to about 50 mS/m, such as up to about 5 mS/m, such as up to about 10 pS/m.

35. The method of any one of claims 31-34, wherein said method comprises

• feeding said portion of said electrically conductive fluid into said

measuring zone;

• closing said inflow tube by said inflow valve arrangement and closing said outflow tube by said outflow tube arrangement,

• purging at least a section of said inflow tube upstream to said inflow valve arrangement and at least a section of said outflow tube downstream to said outflow valve arrangement

• performing said at least one NMR reading on said portion of electrically conductive fluid,

• opening said outflow tube by said outflow tube arrangement, and

• withdrawing said portion of electrically conductive fluid from said

measuring zone via said outflow tube.

36. The method of claim any one of claims 31-35, wherein said method comprises performing a NMR measurement on two or more consecutive portions of said electrically conductive fluid, said method comprises

• feeding a first portion of said electrically conductive fluid into said

measuring zone via said inflow tube;

• purging at least a section of said inflow tube upstream to said inflow valve arrangement and at least a section of said outflow tube

downstream to said outflow valve arrangement

• performing said at least one NMR reading on said first portion of

electrically conductive fluid,

• opening said outflow tube by said outflow tube arrangement, and

• feeding a second portion of said electrically conductive fluid into said measuring zone via said inflow tube while simultaneously withdrawing said first portion of electrically conductive fluid from said measuring zone via said outflow tube, and repeating the measuring sequence.

37. The method of claim any one of claims31-36, wherein said electrically conductive fluid is an aqueous solution, dispersion or suspension, such as a waste water sludge, manure, an ionic solution or a suspension of solid matter, such as particles and/or fibers.

38 . The method of any one of claims 31-37, wherein the inflow tube, the measuring zone tube and the outflow tube form respective sections of a common NMR tube forming a flow through tube and the method comprises performing NMR readings on a sample in a semi flowing condition, comprising holding a sample portion quiescent in the measuring zone during NMR reading.

39. The method of any one of claims 31-38, wherein the method

comprises calibrating the NMR spectrometer by calibration liquid comprising known quantities of 1H isotopes and/or 170 isotopes, the method comprising pumping the calibration liquid into the measuring zone and performing at least one IH NMR reading and/or at least one 170 NMR reading obtaining at least one spectra and correlating the at least one spectra to the known quantities of IH isotopes and/or 170 isotopes, preferably said calibration liquid is water (calibration water).