WO2009103295A1

WO2009103295A1 - An analysis apparatus for in-line monitoring of fluid

Info

Publication number: WO2009103295A1
Application number: PCT/DK2009/000044
Authority: WO
Inventors: Serguei Chiriaev; Rasmus Banke
Original assignee: Danfoss A/S
Priority date: 2008-02-22
Filing date: 2009-02-19
Publication date: 2009-08-27

Abstract

An analysis apparatus (1) for analysing fluid is disclosed. The apparatus (1) comprises a fluid communication system (3) connected to a fluid medium (7), having a first pressure, P₁, via a connector (5). The apparatus (1) further comprises at least one reagent container (8) comprising a first volume (10a) and a second volume (10c). The first volume (10a) contains reagent and is fluidly connected to a detection unit having a second pressure, P₂. The second volume (10c) is fluidly connected to the fluid communication system (3), and therefore has pressure P₁. The second pressure is lower than the first pressure, P₂<P-₁, and the reagent container (8) is arranged to deliver reagent in response to this pressure difference. The pressure difference also drives the collection of sample fluid (11), and thereby the ratio of sample fluid (11) and reagent reaching a detection unit (9, 19) is independent of fluctuations in one or both of the pressures, P₁ and P₂.

Description

AN ANALYSIS APPARATUS FOR IN-LINE MONITORING OF FLUID

FIELD OF THE INVENTION

The present invention relates to an apparatus for performing in-line analysis on fluids flowing in a flow system, in particular for in-line determination of the amount of soluble matter in a liquid contained in lines and systems. More particularly the invention relates to measurements of amounts of soluble matter in water, e.g. amounts of magnesium or calcium in water flowing in pipes or tubes of industrial water systems, water softeners, household machines, such as washing machines, dish washers, etc.

BACKGROUND OF THE INVENTION

Fluid analysers may be used for controlling chemical and biological processes, such as the treatment of sewage water. They may also be used for monitoring the amount or concentration of specific soluble matter contained in a fluid being analysed, e.g. the amount of calcium and/or magnesium in water. This is sometimes desirable because the amounts of calcium and magnesium in water flowing in an industrial water system may damage expensive equipment. Moreover, determination of amounts of calcium and magnesium optimise softening systems.

US 5,672,319 discloses a fully functional analysing unit included within a fluid-tight housing of a dialyzer which is immersed in the medium to be analysed. An opening in the housing is closed by a dialysis membrane. A channel defining body cooperates with the membrane to define a flow channel. The unit includes a carrier fluid reservoir and a carrier pump for generating a flow of carrier fluid through the flow channel. US 5,695,719 discloses a fully functional analysing unit included within a fluid-tight housing of a dialyzer. The self-contained unit includes a carrier fluid reservoir and a carrier pump for generating a flow of carrier fluid through the flow channel to allow transfer of ions and molecules between a medium and the carrier fluid across a membrane. As a result, the flow of carrier fluid is transformed into a flow of sample fluid which is received in a reaction channel. Reagent fluid from at least one reagent reservoir is delivered to the reaction channel by at least one reagent pump, and a detection device is coupled to the reaction channel for detecting a reaction product originating from a reaction between the reagent fluid and the sample fluid and for generating a corresponding detection signal.

US 6,120,736 discloses an analysis apparatus for carrying out chemical analyses. The apparatus has a base member in which there is at least one channel, and it has at least one functional element which is in fluid or gaseous connection with the channel. Pumps are required to set the individual fluids moving in order to mix them with one another or to bring them to a different location.

All of the systems described above require pumps in order to operate properly. Thereby the systems have energy consumption corresponding at least to the energy consumption of the required pumps, and the pumps require maintenance and increase the costs of manufacturing the system. Furthermore, in order to ensure a uniform mixture of sample fluid and reagent, which is required in order to obtain reliable measurements, the flows of sample fluid and reagent, respectively, must be controlled very accurately and in dependence of each other. Therefore relatively complex and precise control systems must be used for controlling the pumps, e.g. using some kind of feedback mechanism. This is cumbersome and relatively expensive, and it still leaves a risk that the obtained mixture of sample fluid and reagent is not completely uniform, thereby putting an upper limit on the obtainable accuracy of the measurements performed by the system.

SUMMARY OF THE INVENTION

It is, thus, an object of the invention to provide an analysis apparatus for analysing a fluid, in which more reliable measurements can be obtained than by using similar prior art apparatuses.

It is a further object of the invention to provide an analysis apparatus for analysing a fluid, in which uniform mixing of sample fluid and reagent can be ensured easily.

It is an even further object of the invention to provide an analysis apparatus for analysing a fluid, in which the energy consumption is reduced as compared to similar prior art apparatuses.

It is an even further object of the invention to provide an analysis apparatus for analysing a fluid, in which the required maintenance to the apparatus is reduced as compared to similar prior art apparatuses.

It is an even further object of the invention to provide an analysis apparatus for analysing a fluid, in which the number of components can be reduced as compared to similar prior art apparatuses.

It is an even further object of the invention to provide an analysis apparatus for analysing a fluid, in which the manufacturing costs can be reduced as compared to similar prior art apparatuses.

According to the invention the above and other objects are fulfilled by providing an analysis apparatus for analysing a fluid, the analysis apparatus comprising: - a fluid communication system arranged in an interior part of the analysis apparatus, said fluid communication system providing fluid communication between parts of the analysis apparatus,

- a connector arranged to establish a fluid connection between a fluid medium having a first pressure, Pi, and the fluid communication system,

- a detection unit adapted to receive and mix sample fluid and reagent, analyze said mixed fluid and generate output, said detection unit having a pressure, P2, and

- at least one reagent container, each reagent container comprising a first volume for containing reagent, said first volume being fluidly connected to the detection unit, and a second volume, said second volume being fluidly connected to the fluid communication system, said reagent container being arranged to deliver reagent in response to a pressure difference between the first volume and the detection unit,

wherein the second pressure is lower than the first pressure, P₂<Pi-

In the present context the term 'analysis apparatus' should be interpreted to mean an apparatus which is adapted to perform analysis on a fluid medium, e.g. with respect to concentrations of certain substances, such as magnesium (Mg), calcium (Ca), biomolecules, bacteria, etc., present in the fluid.

The fluid to be analysed is preferably a liquid, but may, alternatively, be a gaseous fluid. The fluid communication system provides fluid communication between parts of the analysis apparatus, e.g. via a system of pipes and/or tubes interconnecting the various parts in a desired manner.

The connector establishes a fluid connection between a fluid medium to be analysed and the fluid communication system. Thereby sample fluid is collected to the analysis apparatus, more specifically into the fluid communication system. Since the connector interconnects the fluid medium, having a first pressure, Pi, and the fluid communication system, the fluid communication system adapts the pressure of the fluid medium, Pi . Accordingly, the pressure of the interior of the fluid communication system will fluctuate along with possible fluctuations of the pressure of the fluid medium.

The output generated by the detection unit preferably corresponds to the result of the analysis performed on the mixed fluid of sample fluid and reagent, e.g. indicating the amount of a specific substance of interest present in the fluid medium being analysed. The output may be in the form of an optical signal, an electrical current signal, a voltage signal, or any other suitable kind of signal.

The reagent container comprises a first volume and a second volume. The first volume contains reagent and is fluidly connected to the detection unit, and thereby reagent can be delivered from the first volume of the reagent container to the detection unit. The detection unit has a second pressure, P₂-

The detection unit may advantageously be connected to the exterior of the analysis apparatus, e.g. via an opening, preferably arranged in a sink for collecting used sample fluid. In this case the second pressure, P₂, is preferably at or near atmospheric pressure. The second volume is fluidly connected to the fluid communication system, and thereby the pressure of the second volume is the same as the pressure of the fluid communication system, P₁. Since the second pressure is lower than the first pressure, P2<Pi, a pressure difference exists between the second volume of the reagent container and the detection unit, the higher pressure being in the second volume, and this pressure difference causes reagent to be delivered from the reagent container.

Simultaneously, the same pressure difference exists between the connector and the detection unit and is used for driving sample fluid to the detection unit via the fluid communication system. Accordingly, the ratio of the flow rate of sample fluid reaching the detection unit and the flow rate of reagent reaching the detection unit remains invariant, regardless of possible fluctuations in one or both of the pressures, Pi and P₂. Thus a reliable mixture, and thereby reliable measurements, is automatically obtained, and there is no need for complicated feedback mechanisms or the like. Furthermore, it is not necessary to use pumps in order to cause reagent and/or sample fluid to flow in the analysis apparatus, and thereby energy can be saved, required maintenance of the apparatus can be reduced, and manufacturing costs can be reduced due to the lower component count of the apparatus.

The detection unit may comprise a mixing subsystem adapted to receive and mix sample fluid and reagent, and a separate detection part being fluidly connected to the mixing subsystem and being adapted to analyze the mixed fluid and to generate a corresponding output. According to this embodiment, sample fluid and reagent are received and mixed in a separate part of the detection unit, i.e. the mixing subsystem. Once the sample fluid and the reagent have been properly mixed, the mixed fluid is delivered to the detection part where it is analysed. As an alternative, the detection unit may comprise only a single part in which the mixing of the reagent and the sample fluid, as well as the subsequent analysis takes place.

The fluid communication system may comprise at least one flow restrictor arranged in a flow path defined by the fluid communication system. According to this embodiment, the flow rates of the fluid flows of various parts of the fluid communication system can be controlled by arranging flow restrictors of suitable flow resistance in selected parts of the fluid communication system.

According to one embodiment at least one flow restrictor may be arranged in a part of the fluid communication system which fluidly interconnects the connector and the detection unit. According to this embodiment the flow rate of sample fluid reaching the detection unit is controlled. Alternatively or additionally, at least one flow restrictor may be arranged in a part of the fluid communication system which fluidly interconnects the connector and a waste chamber or a sink. A flow restrictor arranged in this manner ensures fast response times of the analysis system.

The analysis apparatus may further comprise a sink being fluidly connected to the fluid communication system, and at least one flow restrictor may be arranged in a part of the fluid communication system which fluidly interconnects the connector and the sink. The sink is used for collecting sample fluid from the analysis apparatus, and it is preferably fluidly connected to the exterior of the analysis apparatus in such a manner the pressure of the sink is substantially the same as the exterior pressure. According to this embodiment the fluid connection between the connector and the sink may advantageously drive fluid into the analysis apparatus, thereby ensuring a substantially constant fluid flow in the fluid communication system. This helps in reducing response times of the apparatus.

Alternatively or additionally, the analysis apparatus may further comprise at least one flow restrictor arranged between the first volume of at least one reagent container and the detection unit. According to this embodiment the flow rate of reagent flowing from the reagent container to the detection unit is controlled.

At least one movable wall may separate the first volume and the second volume of at least one of the reagent containers. According to this embodiment the pressure difference between the second volume and the detection unit, being fluidly connected to the first volume, causes the movable wall to move in such a manner that the first volume is 'squeezed'. Thereby reagent is squeezed out of the first volume and towards the detection unit. The movable wall may advantageously be in the form of a resilient wall. In this case the first volume may, e.g., be a bag or the like arranged inside the second volume. Alternatively, the movable wall may be a relatively rigid wall, e.g. being movable in a manner similar to a piston.

The analysis apparatus may further comprise a pressure reduction system for reducing the first pressure, Pi, as compared to a pressure of an interior part of a flow system having a fluid medium to be analyzed flowing therein. Thereby the pressure difference defining the flow rates of sample fluid and reagent, respectively, can be reduced, and the flow rates can thereby be controlled. This is, e.g., an advantage in the case that the fluid medium has a relatively high pressure.

The pressure reduction system may comprise a reduction chamber with a compliance chamber having one or more movable walls arranged therein. The movable walls may, e.g., be in the form of walls made of a resilient material.

The analysis apparatus may further comprise at least one temperature controlling element. The viscosity of fluids is very often dependant on the temperature of the fluid. Thus, in order to control the flow rates of the sample fluid and the reagent, it is desirable to be able to control the temperature of the fluids flowing in the analysis apparatus. This can be obtained by arranging at least one temperature controlling element in the analysis apparatus. The temperature controlling element(s) may comprise a heating element and/or a cooling element.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail with reference to the accompanying drawing in which

Fig. 1 is a schematic view of an analysis apparatus according to a first embodiment of the invention, and

Fig. 2 is a schematic view of an analysis apparatus according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of an analysis apparatus 1 according to a first embodiment of the invention. The analysis apparatus 1 comprises a dosing reaction part 2 enclosing a fluid communication system 3 in the form of a number of pipes fluidly interconnecting various components of the analysis apparatus 1. The fluid communication system 3 is fluidly connected to a flow system in the form of a pipe 4, via a connector 5 inserted in the pipe 4. A filter 6 is arranged in the connector 5 in order to prevent impurities and unwanted particles from entering the analysis apparatus 1. A liquid 7 to be analysed flows in the pipe 4.

Inside the dosing reaction part 2 two reagent containers 8 and a mixing and reaction subsystem 9 are arranged. Each of the reagent containers 8 comprises a first volume 10a containing reagent. The first volumes 10a have flexible walls 10b, and each is arranged within a rigid wall of a respective reagent container 8 in such a manner that a second volume 10c is defined between the first volume 10a and the rigid walls. The second volume 10c is fluidly connected to the fluid communication system 3.

The pressure in the interior of the fluid communication system 3 is the same as the pressure of the liquid 7, P₁. Pi is higher than an exterior pressure, P₂, occurring outside the analysis apparatus 1.

The analysis apparatus 1 of Fig. 1 may preferably be operated in the following manner. Due to the pressure difference between P₁ and P₂, some liquid, in the following denoted sample fluid 11 , is sucked from the pipe 4 into the fluid communication system 3 via the connector 5. Some of the sample fluid 11 flows into each of the second volumes 10c of the reagent containers 8, via flow paths 12, the second volumes 10c thereby adopting the pressure P₁. The first volumes 10a are fluidly connected to the mixing and reaction subsystem 9 having a pressure P₂, and thereby the flexible walls 10b of the first volumes 10a are squeezed, thereby causing reagent to flow from the first volumes 10a towards the mixing and reaction subsystem 9 via flow paths 13 and flow restrictors 14. The flow rate of the reagent is determined by the pressure difference (P₁-P₂) and by the flow resistance of flow restrictors 13 in accordance with the formula P - P

F. =

R n Simultaneously, some of the sample fluid 11 flows via the fluid communication system and flow restrictor 15 into the mixing and reaction subsystem 9. The flow rate is determined by the pressure difference (Pr P₂) and the flow resistance of the flow restrictor 15 in accordance with the

P - P formula F_sample = — . Accordingly, reagent and sample fluid 11 is mixed sample in the mixing and reaction subsystem 9, and chemical reactions between the reagent and the sample fluid 11 takes place if specific soluble matter is present in the sample fluid 11.

Since the flow rates of reagent and sample fluid 11 into the mixing and reaction subsystem 9 are all determined by the pressure difference, P1-P₂, the ratio of the flow rate of reagent and the flow rate of sample fluid 11 remains substantially constant, even in case of variations in the pressure difference or one or both of the pressures. Thereby it is ensured that the relative concentration of reagent and sample fluid 11 in the mixing and reaction subsystem 9 is substantially uniform, and very reliable measurements can thereby be obtained, without the requirement of pumps and complicated feedback mechanisms.

Finally, some of the sample fluid 11 flow directly into waste container 16, via flow restrictor 17, and further into sink 18 arranged exterior of the analysis apparatus 1. The sink 18 is provided with an opening 18a providing communication between the sink 18 and the exterior of the analysis apparatus 1. Accordingly, the pressure inside the waste container 16 is the same as the exterior pressure, i.e. P₂. Since the mixing and reaction subsystem 9 is fluidly connected to the waste container 16, the pressure inside the mixing and reaction subsystem 9 is also P₂.

Still driven by the pressure difference, Pi-P₂, the mixed and reacted fluid flows into detection part 19. The detection part 19 generates a response signal in response to the reacted compounds present in the mixed and reacted fluid. Accordingly, the response signal is representative for the concentration of a specific soluble compound in the sample fluid 11 , and thereby the concentration of this soluble compound in the liquid 7 flowing in the pipe 4.

Fig. 2 is a schematic view of an analysis apparatus 1 according to a second embodiment of the invention. The parts of the embodiment shown in Fig. 1 are also present in the embodiment shown in Fig. 2, and they will therefore not be described in further detail here. The analysis apparatus 1 of Fig. 2 is further provided with a pressure reduction system used for reducing the pressure inside the fluid communication system 3 from the pressure, Pi, occurring in the pipe 4 to a working pressure, P_w. The pressure reduction system comprises a valve 20 arranged to fluidly connect the connector 5 and a reduction chamber 21 with a compliance chamber 22 having one or more flexible walls. The compliance chamber 22 contains air or a gas. A pressure transmitter 23 measures the pressure in the reduction chamber 21. An electronic circuit 24 controls the status of the valve 20, i.e. open or closed status, according to the pressure measured by the pressure transmitter 23. The pressure transmitter 23 and the valve 20 are connected to the electronic circuit 24 via electrical connections 25.

The pressure reduction system may preferably operate in the following manner. A working pressure, P_Wl is maintained in an interval between a lower set point value, Pi_0Wer, and an upper set point value, P_upPer- When the pressure in the reduction chamber 21 , and thereby in the fluid communication system 3, reaches the lower set point value, Pi_ower, the control circuit 24 causes the valve 20 to open, and sample fluid 11 thereby flows into reduction chamber 21 until the pressure in the reduction chamber 21 reaches the upper set point value, P_upPer- At this point the control circuit 24 causes the valve 20 to close, thereby disrupting the flow of sample fluid 11. The discharge of the first volumes 10 of the reagent containers 8 results in reduction of the pressure in the fluid communication system 3, and thereby in the reduction chamber 21 , until the lower set point value, Piow_er, is once again reached, and the cycle described above is repeated. The compliance chamber 22 is embedded in the reduction chamber 21 in order to adjust the compliance of the reduction system to a value required for an optimal operation of the apparatus 1.

Claims

1. An analysis apparatus for analysing a fluid, the analysis apparatus comprising:

- a fluid communication system arranged in an interior part of the analysis apparatus, said fluid communication system providing fluid communication between parts of the analysis apparatus,

wherein the second pressure is lower than the first pressure, P₂<Pi-

2. An analysis apparatus according to claim 1 , wherein the detection unit comprises a mixing subsystem adapted to receive and mix sample fluid and reagent, and a separate detection part being fluidly connected to the mixing subsystem and being adapted to analyze the mixed fluid and to generate a corresponding output.

3. An analysis apparatus according to claim 1 or 2, wherein the fluid communication system comprises at least one flow restrictor arranged in a flow path defined by the fluid communication system.

4. An analysis apparatus according to claim 3, wherein at least one flow restrictor is arranged in a part of the fluid communication system which fluidly interconnects the connector and the detection unit.

5. An analysis apparatus according to claim 3 or 4, further comprising a sink being fluidly connected to the fluid communication system, and wherein at least one flow restrictor is arranged in a part of the fluid communication system which fluidly interconnects the connector and the sink.

6. An analysis apparatus according to any of the preceding claims, further comprising at least one flow restrictor arranged between the first volume of at least one reagent container and the detection unit.

7. An analysis apparatus according to any of the preceding claims, wherein at least one movable wall separates the first volume and the second volume of at least one of the reagent containers.

8. An analysis apparatus according to any of the preceding claims, further comprising a pressure reduction system for reducing the first pressure, P₁, as compared to a pressure of an interior part of a flow system having a fluid medium to be analyzed flowing therein.

9. An analysis apparatus according to claim 8, wherein the pressure reduction system comprises a reduction chamber with a compliance chamber having one or more movable walls arranged therein.

10. An analysis apparatus according to any of the preceding claims, further comprising at least one temperature controlling element.