CA2095957A1 - Measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratio - Google Patents
Measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratioInfo
- Publication number
- CA2095957A1 CA2095957A1 CA002095957A CA2095957A CA2095957A1 CA 2095957 A1 CA2095957 A1 CA 2095957A1 CA 002095957 A CA002095957 A CA 002095957A CA 2095957 A CA2095957 A CA 2095957A CA 2095957 A1 CA2095957 A1 CA 2095957A1
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- Prior art keywords
- mixture
- measuring
- liquid
- dry matter
- process pipe
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 78
- 239000000203 mixture Substances 0.000 title claims abstract description 74
- 239000007788 liquid Substances 0.000 title claims abstract description 41
- 230000008569 process Effects 0.000 claims abstract description 63
- 230000005684 electric field Effects 0.000 claims abstract description 11
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 230000001681 protective effect Effects 0.000 claims description 14
- 230000010363 phase shift Effects 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 5
- 238000005259 measurement Methods 0.000 claims description 2
- 238000009740 moulding (composite fabrication) Methods 0.000 abstract 1
- 239000000126 substance Substances 0.000 description 7
- 239000002184 metal Substances 0.000 description 5
- 230000005855 radiation Effects 0.000 description 5
- 230000002285 radioactive effect Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D11/00—Component parts of measuring arrangements not specially adapted for a specific variable
- G01D11/24—Housings ; Casings for instruments
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/06—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a liquid
- G01N27/07—Construction of measuring vessels; Electrodes therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
Landscapes
- Chemical & Material Sciences (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Electrochemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Dispersion Chemistry (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
Abstract A measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratio. The device is a thin blade-like rod (1) arranged in a process pipe (3), the device form-ing an electric field with a frequency varying within a certain range between the electrode (2) and the pro-cess and the process pipe (3), which functions as the second electrode. In the method an alternating current having a fixed frequency is conducted through the liquid/dry matter mixture, whereby the proportions of capacitive and resistive current can be determined on the basis of the phase difference of current caused by the liquid/dry matter mixture. Thereby the proportion of capacitive current describes the liquid/dry matter mixture ratio and the proportion of resistive current describes the impurities occurring in the mixture.
(Fig. 1)
(Fig. 1)
Description
-- 209~957 A measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratio The invention relates to a measuring device for measuring the liquid/dry matter mixture ratio in a mixture flowing in a process pipe, the measuring device comprising a rod-shaped measuring electrode installed in the middle of the process pipe and parallel thereto, fastening means for fastening the measuring device to the process pipe and a connection box protecting the electronics unit for measuring, an AC electric field of 1 to 100 MHz being formed for measurement between the measuring electrode and the process pipe.
The invention also relates to a method of determining the liquid/dry matter mixture ratio, wherein a high frequency electric current of 1 to 100 MHz is conducted through the mixture and the amplitude of the current passing through the mixture is measured.
In conventional measuring arrangements the mixture ratio of liquid to dry matter has been measured by sampling the liquid/dry matter mixture to be measured or by using continuously operating pairs of transmit~
ting/receiving means based e.g. on radioactive radi-ation. When radiation exposure is measured, part of the radiation transmitted is scattered and reflected from the substance measured, while part of it passes through the substance measured and reaches the receiving means.
The liquid/dry matter mixture ratio can then be con-cluded directly from the amount of radioactive radiation that has reached the receiving means. Infrared and optical measuring are also performed on a similar prin-ciple. In several situations pairs of transmitting-/receiving means based on microwave radiation have also been used. However, measuring arrangements of this kind . ~ .. ~ .: -- - .
.
209~957 are very expensive and fragile in process conditions.
Further, process conditions have a great effect on the accuracy of measuring devices, whereby every system of measuring devices has to be calibrated separately according to the process concerned. It is also to be noted that measuring performed e.g. by radioactive radiation is very detrimental to the environment. Con-ventionally, problems have arisen in situations where the dry matter content of the mixture is very high, whereas the quantity of liquid in the mixture is small.
In conditions where the pressure is high and the quantity of liquid is small, the liquid often occurs in different phases. The accuracy of the measuring devices concerned is then not sufficient to control the process, whereby they cannot determine the accurate liquid con-tent of the mixture. Further, as a result of variations in the colour of the mixture, measuring devices based e.g. on optical or infrared measuring often give in-correct information on the liquid/dry matter mixture ratio. The accurate liquid/dry matter mixture ratio can be determined by taking individual samples of the mix-ture and subsequently separating the liquid from the dry matter, but with regard to process control the method is much too slow to produce a preparation of uniform quality.
DE 2,412,165 discloses a method and apparatus for measuring the solid matter concentration in a mix-ture. In the method an alternating current is conducted through the mixture, whereby the solid matter content of the mixture can be concluded from the amplitude of the current that has passed through the mixture. The publication discloses an apparatus for carrying out the method. The apparatus is circular in cross-section, two plate electrodes being arranged within the circle paral-lel to each other. The whole unit is then disposed in : :.:., ~ ~; . , . . . , , ,. : - . .
2Q9~57 the process pipe as close as to the middle of the pipe line as possible. The plate-like planes function as charging plates for the capacitor, and an electric field with a varying frequency is formed between the plates.
The medium between the plates and the insulating capa-city and permeability of the medium vary with the different substances passed between the plate planes.
The current moving from one plate electrode to another is determined by the permeability of the substance between the plates.
The apparatus in question brings about a high flow resistance in the process pipe system and hinders the process. Because of the structure of the apparatus, high flow rates cannot be used since in a high rate flow the measuring apparatus might be easily distorted in the process pipe system. Further, servicing of the apparatus in question is very difficult, practically impossible, since it is extremely difficult to detach it from the process pipe system.
DE 4,037,320 discloses an apparatus for meas-uring the concentrations of petrol components. In this apparatus a rod-shaped electrode is arranged in a metal pipe, as close to the middle of the pipe as possible, so that the alternating current field formed between the metal pipe and the rod is as uniform as possible. How-ever, the problem is that the rod-shaped electrode is arranged at a point where the pipe forms an angle of 90. When the rod-shaped electrode is arranged in the pipe, part of it aligns with the section of the pipe that is perpendicular thereto, whereby the electric field is not homogeneous but very inhomogeneous. This makes measuring inaccurate. It is also to be noted that if the apparatus is used with mixtures containing solid matter and if the flow comes directly to the end of the flow pipe to which the rod-shaped electrode is attached, 209~957 the apparatus is exposed to high pressure. It is ~hen very difficult to seal the rod electrode against the end of the pipe. High pressure quickly wears the sealing means between the pipe end and the rod electrode. It is also to be noted that excess dirt occurring in the liquid easily accumulates at the pipe end and makes measuring inaccurate and unreliable.
DE 1,263,354 discloses a measuring system for measuring the concentration of a mixture. This system is based on two plane electrodes arranged in a flow pipe. Thus the system is very similar to the solution of DE 2,421,165. The above disadvantages of the solution of DE 2,412,165 are also found in the apparatus of DE
l,263,354.
The object of the present invention is to improve the method of measuring a liquid/dry matter mix-ture and further to develop a more reliable measuring device for process conditions.
The apparatus of the invention is characterised in that the measuring electrode of the measuring device is arranged in the direct section of the process pipe and that between the measuring electrode and the fasten-ing means is a protective element for removing an elec-tric stray field.
The method of the invention is characterised by further measuring the phase shift between the current and the supply voltage caused by the mixture, and by determining the capacitive and resistive conductance of the mixture from the amplitude of the current and from the phase shift, the liquid/dry matter ratio of the mixture being determined from the capacitive component and the purity of the mixture being determined from the resistive component.
An essential idea of the invention is that a detector measuring the liquid/dry matter mixture ratio . .: . - . , . :.
.. ,. , - . . ,, ,, ,, ~. . ~ , 2~9~ 7 is arranged in the middle of the process pipe and that the rod-shaped electrode attached to the process pipe is coated at a sufficiently long distance from the point of attachment of the electrode towards the tip thereof with a substance having a good insulating capasity. It is thus ensured that the electric field between the rod-shaped electrode and the pipe is homogeneous since the electric field-forming part of the electrode is arranged in the direct section of the process pipe. Another essential idea is that the insulating substance of the rod electrode in the process pipe is blade-shaped so that it controls the flow of the mixture, causing as little flow resistance as possible. A further essential idea is that the rod electrode is attached to the pro-cess pipe by a clamp, whereby the joint is very tight and the rod-shaped electrode is easy to service. It is also to be noted that the blade-shaped insulation/flow controller is held clean by arranging the rod-shaped electrode in the process pipe towards the flow direc-tion.
The essential idea of the method is that when a current with a constant frequency is supplied, the variation in the liquid/dry matter mixture ratio causes dielectric variation between the rod electrode and the process pipe. Thus, the impedance of the mixture can be determined by measuring the phase shift of current between the rod-shaped electrode and the process pipe, the real part representing the resistive conductance i while the imaginary part represents the capacitive conductance. From the resistive conductance can be con-cluded the presence of impurities, such as salts and other corresponding ionizable substances, that should not occur in the mixture. Correspondingly, from the capacitive conductance can be concluded the liquid/dry matter ratio of the mixture. The essential advantage is --` 209~7 that the properties of the mixture used in the process can be determined much more accurately, whereby the mixture can be controlled much more accurately. Further, it is also possible to conclude the relative amount of bases on the one hand and acids on the other hand.
In the following the invention is described in greater detail with reference to the drawing, wherein Fig. 1 shows a partly cross-sectional view of a measuring device according to the invention arranged in a process pipe, Fig. la shows a measuring device according to the invention as seen from the flow direction, Fig. 2 shows another embodimeint of the measuring device according to the invention arranged in a process pipe, and Fig. 2a shows another measuring device accord-ing to the invention as seen from the flow direction.
A measuring device 1 of Fig. 1 comprises a measuring electrode 2, a mixture 4 of liquid and dry matter flowing in a process pipe 3, a process pipe 3 and an electronics unit 5 for measuring arranged in a con-nection box 6. The electronics unit 5 for measuring is supplied by a cable 7 and via the same cable 7 the mea-suring data can be transmitted to the control consoles or possibly to the process computer. Between the mea-suring electrode 2 and the connection box 6 is arranged a protective blade 8 made of material having a small di-electric constant, the blade being arranged to prevent the formation of a stray field and to support the mea-suring electrode 2. Thereby the electric field does not become inhomogeneous but an electric field 9 is formed only between the measuring electrode 2 and the process pipe 3 as a homogeneous field. Fig. 1 further shows an electric field 9 formed between the measuring electrode 2 and the process pipe 3 when the flow pipe is connected . -. . . '' . ~ .. I ' ' ' ' 209~9~7 to the electronics unit for measuring by means of a metal sleeve 10. Advantageously, the measuring device 1 is fastened to the process pipe 3 by an attachment clamp, fastening means necessary for a clamp being machined to the process pipe 3 and the metal sleeve 10.
Thus the rod electrode concerned is easy to detach from the process pipe for servicing and in a critical situ-ation, e.g. in case of malfunction, it can also be removed and the mounting hole in the process pipe 3 can be closed with a separate blind plate. The cylindrical protective blade 8 is tightly attached to the neck of the measuring electrode 2, whereby it also functions as a seal, preventing the mixture 4 of liquid and dry matter from penetrating into the electronics unit 5 for measuring. Further, the shape of the protective blade 8 greatly reduces the flow resistance of the measuring device 1. The blade-like shape controls the flow in such a way that material occurring in the process mixture does not accumulate at the point of contact of the mea-suring device 1 and the process pipe 3 and that the joint between the measuring device 1 and the process pipe 3 is held clean. The electronics unit 5 measures the amplitude of the current passing through the mixture 4 of liquid and dry matter and the phase shift of cur-rent caused by the mixture 4. Thus, the electric circuit comprises a measuring electrode 2, a mixture 4 of liquid and dry matter, a process pipe 3, a metal sleeve 10 and an electronics unit 5. As the ratio of liquid to dry matter in the mixture 4 varies, the electric insulating capacity of the liquid/dry matter mixture flowing in the process pipe 3 changes. On the basis of the phase shift of current caused by the liquid/dry matter mixture 4 can be determined the impedance of the liquid/dry matter mixture 4, the real part of the impedance representing the resistivity of the mixture 4 while the imaginary ~: .
' ~ : ' ~, , -~ 209~957 part represents the capacitivity of the mixture 4. In order that the electric field 9 between the measuring electrode 2 and the process pipe 3 mig~t be rendered symmetric, the measuring electrode 2 must be arranged as close to the middle of the process pipe 3 as possible and parallel thereto. Advantageously, the measuring device 1 is arranged in the process pipe 3 towards the flow direction, arrow A in Fig. 1 indicating the flow direction of the liquid/dry matter mixture 4. The elec-tronics unit 5 need not be arranged in the connection box 6, whereby the structure of the measuring electrode 2 is greatly simplified and the electrode does not con-tain an electronics unit that is damaged in demanding process conditions. In addition, the electronics unit 5 may convert the measuring result directly from the values of capacitive and resistive impedance to dry matter content and impurity content of the liquid/dry matter mixture when the total flow of the material is known. Further, measuring can be performed by conven-tional analogy techniques but the use of digital tech-niques is also possible, the electronics unit 5 then communicating directly with the process computer. The message is then formed either by serial or parallel communication.
Fig. la shows the measuring device 1 as seen from the flow direction. The numbers in Fig. la corre-spond to the numbers in Fig. 1. The protective blade 8 is as thin as possible perpendicular to the pipe curve radius, whereby the flow resistance of the measuring device 1 is as small as possible. However, the measuring electrode 2 is supported sufficiently, whereby it stays in the middle of the process pipe 3 and does not move therefrom due to flow.
Fig. 2 shows a measuring device 1, which is to b~ installed in the direct process pipe 3. The numbers 209~9~
in Fig. 2 also correspond to the numbers in Fig. 1. The measuring device 1 is fastened to the process pipe 3 by attaching a collar 11 to the process pipe 3. Thereby it is possible to arrange attachment clamps around the sleeve 10, the clamps fastening the sleeve tightly against the collar 11. Further, the measuring device 1 is such that the measuring electrode 2 is perpendicular to the body of the measuring device 1, the measuring electrode 2 being essentially parallel to the process pipe 3 and arranged in such a way that the measuring electrode 2 lies midway of the process pipe 3. The pro-tective blade 8 is arranged to prevent a stray field between the measuring electrode 2 and the body of the measuring device 1, the electric field 9 being as homo-geneous as possible in respect of the process pipe 3.
The protective blade 8 is shaped in such a way that it provides as little flow resistance as possible to the mixture. Therefore, it has been made a thin blade-shaped element perpendicular to the radial direction of the process pipe 3.
Fig. 2a shows a measuring device 1 as seen from the flow direction, particularly showing the thin shape of the protective blade 8 transverse to the flow direc-tion.
It is known per se to distribute current into components by means of phase difference but it is new to use the phase difference to determine the dry matter ratio and impurities of a flowing mixture, thereby improving process control. Particularly in a situation where the measuring system is arranged in a control loop where an alternating component modulates to a certain level of the liquid/dry matter mixture ratio, a small separate control valve can be connected to the system, the valve being very quick to control the ratio of the . ; , . . , . :
. ~ .. . ~ . . . ,... . ~.. : .
, ~..... , . . . ::
2 ~ 7 mixture due to its size and thereby improving the uni-formity of the mixture.
The drawings and the description relating thereto are to be understood only as illustrating the inventive idea. The measuring device according to the invention may vary in its details within the scope of the claims. Thus, e.g. the frequency of the alternating current used may vary very broadly, and the shape of the measuring electrode may also vary. Thus, the electrode may be ball-shaped or also have any other shape, the shape of the electrode depending on the use and the accuracy desired.
'~ .''
The invention also relates to a method of determining the liquid/dry matter mixture ratio, wherein a high frequency electric current of 1 to 100 MHz is conducted through the mixture and the amplitude of the current passing through the mixture is measured.
In conventional measuring arrangements the mixture ratio of liquid to dry matter has been measured by sampling the liquid/dry matter mixture to be measured or by using continuously operating pairs of transmit~
ting/receiving means based e.g. on radioactive radi-ation. When radiation exposure is measured, part of the radiation transmitted is scattered and reflected from the substance measured, while part of it passes through the substance measured and reaches the receiving means.
The liquid/dry matter mixture ratio can then be con-cluded directly from the amount of radioactive radiation that has reached the receiving means. Infrared and optical measuring are also performed on a similar prin-ciple. In several situations pairs of transmitting-/receiving means based on microwave radiation have also been used. However, measuring arrangements of this kind . ~ .. ~ .: -- - .
.
209~957 are very expensive and fragile in process conditions.
Further, process conditions have a great effect on the accuracy of measuring devices, whereby every system of measuring devices has to be calibrated separately according to the process concerned. It is also to be noted that measuring performed e.g. by radioactive radiation is very detrimental to the environment. Con-ventionally, problems have arisen in situations where the dry matter content of the mixture is very high, whereas the quantity of liquid in the mixture is small.
In conditions where the pressure is high and the quantity of liquid is small, the liquid often occurs in different phases. The accuracy of the measuring devices concerned is then not sufficient to control the process, whereby they cannot determine the accurate liquid con-tent of the mixture. Further, as a result of variations in the colour of the mixture, measuring devices based e.g. on optical or infrared measuring often give in-correct information on the liquid/dry matter mixture ratio. The accurate liquid/dry matter mixture ratio can be determined by taking individual samples of the mix-ture and subsequently separating the liquid from the dry matter, but with regard to process control the method is much too slow to produce a preparation of uniform quality.
DE 2,412,165 discloses a method and apparatus for measuring the solid matter concentration in a mix-ture. In the method an alternating current is conducted through the mixture, whereby the solid matter content of the mixture can be concluded from the amplitude of the current that has passed through the mixture. The publication discloses an apparatus for carrying out the method. The apparatus is circular in cross-section, two plate electrodes being arranged within the circle paral-lel to each other. The whole unit is then disposed in : :.:., ~ ~; . , . . . , , ,. : - . .
2Q9~57 the process pipe as close as to the middle of the pipe line as possible. The plate-like planes function as charging plates for the capacitor, and an electric field with a varying frequency is formed between the plates.
The medium between the plates and the insulating capa-city and permeability of the medium vary with the different substances passed between the plate planes.
The current moving from one plate electrode to another is determined by the permeability of the substance between the plates.
The apparatus in question brings about a high flow resistance in the process pipe system and hinders the process. Because of the structure of the apparatus, high flow rates cannot be used since in a high rate flow the measuring apparatus might be easily distorted in the process pipe system. Further, servicing of the apparatus in question is very difficult, practically impossible, since it is extremely difficult to detach it from the process pipe system.
DE 4,037,320 discloses an apparatus for meas-uring the concentrations of petrol components. In this apparatus a rod-shaped electrode is arranged in a metal pipe, as close to the middle of the pipe as possible, so that the alternating current field formed between the metal pipe and the rod is as uniform as possible. How-ever, the problem is that the rod-shaped electrode is arranged at a point where the pipe forms an angle of 90. When the rod-shaped electrode is arranged in the pipe, part of it aligns with the section of the pipe that is perpendicular thereto, whereby the electric field is not homogeneous but very inhomogeneous. This makes measuring inaccurate. It is also to be noted that if the apparatus is used with mixtures containing solid matter and if the flow comes directly to the end of the flow pipe to which the rod-shaped electrode is attached, 209~957 the apparatus is exposed to high pressure. It is ~hen very difficult to seal the rod electrode against the end of the pipe. High pressure quickly wears the sealing means between the pipe end and the rod electrode. It is also to be noted that excess dirt occurring in the liquid easily accumulates at the pipe end and makes measuring inaccurate and unreliable.
DE 1,263,354 discloses a measuring system for measuring the concentration of a mixture. This system is based on two plane electrodes arranged in a flow pipe. Thus the system is very similar to the solution of DE 2,421,165. The above disadvantages of the solution of DE 2,412,165 are also found in the apparatus of DE
l,263,354.
The object of the present invention is to improve the method of measuring a liquid/dry matter mix-ture and further to develop a more reliable measuring device for process conditions.
The apparatus of the invention is characterised in that the measuring electrode of the measuring device is arranged in the direct section of the process pipe and that between the measuring electrode and the fasten-ing means is a protective element for removing an elec-tric stray field.
The method of the invention is characterised by further measuring the phase shift between the current and the supply voltage caused by the mixture, and by determining the capacitive and resistive conductance of the mixture from the amplitude of the current and from the phase shift, the liquid/dry matter ratio of the mixture being determined from the capacitive component and the purity of the mixture being determined from the resistive component.
An essential idea of the invention is that a detector measuring the liquid/dry matter mixture ratio . .: . - . , . :.
.. ,. , - . . ,, ,, ,, ~. . ~ , 2~9~ 7 is arranged in the middle of the process pipe and that the rod-shaped electrode attached to the process pipe is coated at a sufficiently long distance from the point of attachment of the electrode towards the tip thereof with a substance having a good insulating capasity. It is thus ensured that the electric field between the rod-shaped electrode and the pipe is homogeneous since the electric field-forming part of the electrode is arranged in the direct section of the process pipe. Another essential idea is that the insulating substance of the rod electrode in the process pipe is blade-shaped so that it controls the flow of the mixture, causing as little flow resistance as possible. A further essential idea is that the rod electrode is attached to the pro-cess pipe by a clamp, whereby the joint is very tight and the rod-shaped electrode is easy to service. It is also to be noted that the blade-shaped insulation/flow controller is held clean by arranging the rod-shaped electrode in the process pipe towards the flow direc-tion.
The essential idea of the method is that when a current with a constant frequency is supplied, the variation in the liquid/dry matter mixture ratio causes dielectric variation between the rod electrode and the process pipe. Thus, the impedance of the mixture can be determined by measuring the phase shift of current between the rod-shaped electrode and the process pipe, the real part representing the resistive conductance i while the imaginary part represents the capacitive conductance. From the resistive conductance can be con-cluded the presence of impurities, such as salts and other corresponding ionizable substances, that should not occur in the mixture. Correspondingly, from the capacitive conductance can be concluded the liquid/dry matter ratio of the mixture. The essential advantage is --` 209~7 that the properties of the mixture used in the process can be determined much more accurately, whereby the mixture can be controlled much more accurately. Further, it is also possible to conclude the relative amount of bases on the one hand and acids on the other hand.
In the following the invention is described in greater detail with reference to the drawing, wherein Fig. 1 shows a partly cross-sectional view of a measuring device according to the invention arranged in a process pipe, Fig. la shows a measuring device according to the invention as seen from the flow direction, Fig. 2 shows another embodimeint of the measuring device according to the invention arranged in a process pipe, and Fig. 2a shows another measuring device accord-ing to the invention as seen from the flow direction.
A measuring device 1 of Fig. 1 comprises a measuring electrode 2, a mixture 4 of liquid and dry matter flowing in a process pipe 3, a process pipe 3 and an electronics unit 5 for measuring arranged in a con-nection box 6. The electronics unit 5 for measuring is supplied by a cable 7 and via the same cable 7 the mea-suring data can be transmitted to the control consoles or possibly to the process computer. Between the mea-suring electrode 2 and the connection box 6 is arranged a protective blade 8 made of material having a small di-electric constant, the blade being arranged to prevent the formation of a stray field and to support the mea-suring electrode 2. Thereby the electric field does not become inhomogeneous but an electric field 9 is formed only between the measuring electrode 2 and the process pipe 3 as a homogeneous field. Fig. 1 further shows an electric field 9 formed between the measuring electrode 2 and the process pipe 3 when the flow pipe is connected . -. . . '' . ~ .. I ' ' ' ' 209~9~7 to the electronics unit for measuring by means of a metal sleeve 10. Advantageously, the measuring device 1 is fastened to the process pipe 3 by an attachment clamp, fastening means necessary for a clamp being machined to the process pipe 3 and the metal sleeve 10.
Thus the rod electrode concerned is easy to detach from the process pipe for servicing and in a critical situ-ation, e.g. in case of malfunction, it can also be removed and the mounting hole in the process pipe 3 can be closed with a separate blind plate. The cylindrical protective blade 8 is tightly attached to the neck of the measuring electrode 2, whereby it also functions as a seal, preventing the mixture 4 of liquid and dry matter from penetrating into the electronics unit 5 for measuring. Further, the shape of the protective blade 8 greatly reduces the flow resistance of the measuring device 1. The blade-like shape controls the flow in such a way that material occurring in the process mixture does not accumulate at the point of contact of the mea-suring device 1 and the process pipe 3 and that the joint between the measuring device 1 and the process pipe 3 is held clean. The electronics unit 5 measures the amplitude of the current passing through the mixture 4 of liquid and dry matter and the phase shift of cur-rent caused by the mixture 4. Thus, the electric circuit comprises a measuring electrode 2, a mixture 4 of liquid and dry matter, a process pipe 3, a metal sleeve 10 and an electronics unit 5. As the ratio of liquid to dry matter in the mixture 4 varies, the electric insulating capacity of the liquid/dry matter mixture flowing in the process pipe 3 changes. On the basis of the phase shift of current caused by the liquid/dry matter mixture 4 can be determined the impedance of the liquid/dry matter mixture 4, the real part of the impedance representing the resistivity of the mixture 4 while the imaginary ~: .
' ~ : ' ~, , -~ 209~957 part represents the capacitivity of the mixture 4. In order that the electric field 9 between the measuring electrode 2 and the process pipe 3 mig~t be rendered symmetric, the measuring electrode 2 must be arranged as close to the middle of the process pipe 3 as possible and parallel thereto. Advantageously, the measuring device 1 is arranged in the process pipe 3 towards the flow direction, arrow A in Fig. 1 indicating the flow direction of the liquid/dry matter mixture 4. The elec-tronics unit 5 need not be arranged in the connection box 6, whereby the structure of the measuring electrode 2 is greatly simplified and the electrode does not con-tain an electronics unit that is damaged in demanding process conditions. In addition, the electronics unit 5 may convert the measuring result directly from the values of capacitive and resistive impedance to dry matter content and impurity content of the liquid/dry matter mixture when the total flow of the material is known. Further, measuring can be performed by conven-tional analogy techniques but the use of digital tech-niques is also possible, the electronics unit 5 then communicating directly with the process computer. The message is then formed either by serial or parallel communication.
Fig. la shows the measuring device 1 as seen from the flow direction. The numbers in Fig. la corre-spond to the numbers in Fig. 1. The protective blade 8 is as thin as possible perpendicular to the pipe curve radius, whereby the flow resistance of the measuring device 1 is as small as possible. However, the measuring electrode 2 is supported sufficiently, whereby it stays in the middle of the process pipe 3 and does not move therefrom due to flow.
Fig. 2 shows a measuring device 1, which is to b~ installed in the direct process pipe 3. The numbers 209~9~
in Fig. 2 also correspond to the numbers in Fig. 1. The measuring device 1 is fastened to the process pipe 3 by attaching a collar 11 to the process pipe 3. Thereby it is possible to arrange attachment clamps around the sleeve 10, the clamps fastening the sleeve tightly against the collar 11. Further, the measuring device 1 is such that the measuring electrode 2 is perpendicular to the body of the measuring device 1, the measuring electrode 2 being essentially parallel to the process pipe 3 and arranged in such a way that the measuring electrode 2 lies midway of the process pipe 3. The pro-tective blade 8 is arranged to prevent a stray field between the measuring electrode 2 and the body of the measuring device 1, the electric field 9 being as homo-geneous as possible in respect of the process pipe 3.
The protective blade 8 is shaped in such a way that it provides as little flow resistance as possible to the mixture. Therefore, it has been made a thin blade-shaped element perpendicular to the radial direction of the process pipe 3.
Fig. 2a shows a measuring device 1 as seen from the flow direction, particularly showing the thin shape of the protective blade 8 transverse to the flow direc-tion.
It is known per se to distribute current into components by means of phase difference but it is new to use the phase difference to determine the dry matter ratio and impurities of a flowing mixture, thereby improving process control. Particularly in a situation where the measuring system is arranged in a control loop where an alternating component modulates to a certain level of the liquid/dry matter mixture ratio, a small separate control valve can be connected to the system, the valve being very quick to control the ratio of the . ; , . . , . :
. ~ .. . ~ . . . ,... . ~.. : .
, ~..... , . . . ::
2 ~ 7 mixture due to its size and thereby improving the uni-formity of the mixture.
The drawings and the description relating thereto are to be understood only as illustrating the inventive idea. The measuring device according to the invention may vary in its details within the scope of the claims. Thus, e.g. the frequency of the alternating current used may vary very broadly, and the shape of the measuring electrode may also vary. Thus, the electrode may be ball-shaped or also have any other shape, the shape of the electrode depending on the use and the accuracy desired.
'~ .''
Claims (6)
1. A measuring device for measuring the liquid/dry matter mixture ratio in a mixture flowing in a process pipe, the measuring device comprising a rod-shaped measuring electrode installed in the middle of the process pipe and parallel thereto, fastening means for fastening the measuring device to the process pipe and a connection box protecting the electronics unit for measuring, an AC electric field of 1 to 100 MHz being formed for measurement between the measuring electrode and the process pipe, wherein the measuring electrode of the measuring device is arranged in the direct section of the process pipe, and between the measuring electrode and the fastening means is a protective element for removing an electric stray field.
2. A device of claim 1, wherein the protective element is made of material having a small dielectric constant.
3. A device of claim 1, wherein the protective element is arranged to align with the curve of the process pipe, and the protective element is a blade-shaped element, thin perpendicular to the pipe curve radius.
4. A device of claim 1, wherein the protective element is a thin element perpendicular to the flow direction of the material in the process pipe.
5. A device of claim 1, wherein the measuring electrode is arranged towards the flow of the mixture, whereby impurities occurring in the mixture do not accumulate in the measuring electrode and protective element.
6. A method of determining the liquid/dry matter mixture ratio, wherein a high frequency electric current of 1 to 100 MHz is conducted through the mixture, and the amplitude of the current passing through the mixture is measured, and further, the phase shift between the current and the supply voltage caused by the mixture is measured, and the capacitive and resistive conductance of the mixture are measured from the amplitude of the current and from the phase shift, the liquid/dry matter ratio of the mixture being deter-mined from the capacitive component and the purity of the mixture being determined from the resistive component.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002095957A CA2095957A1 (en) | 1993-05-11 | 1993-05-11 | Measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratio |
| SE9301633A SE9301633L (en) | 1993-05-11 | 1993-05-12 | Feed device for measuring the liquid-dry mixture ratio and method for determining the liquid-dry mixture ratio |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002095957A CA2095957A1 (en) | 1993-05-11 | 1993-05-11 | Measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratio |
| SE9301633A SE9301633L (en) | 1993-05-11 | 1993-05-12 | Feed device for measuring the liquid-dry mixture ratio and method for determining the liquid-dry mixture ratio |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2095957A1 true CA2095957A1 (en) | 1994-11-12 |
Family
ID=25676166
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002095957A Abandoned CA2095957A1 (en) | 1993-05-11 | 1993-05-11 | Measuring device for measuring the liquid/dry matter mixture ratio and a method of determining the liquid/dry matter mixture ratio |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2095957A1 (en) |
| SE (1) | SE9301633L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019243142A1 (en) * | 2018-06-20 | 2019-12-26 | Ab Sandvik Materials Technology | Tube portion |
-
1993
- 1993-05-11 CA CA002095957A patent/CA2095957A1/en not_active Abandoned
- 1993-05-12 SE SE9301633A patent/SE9301633L/en not_active Application Discontinuation
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019243142A1 (en) * | 2018-06-20 | 2019-12-26 | Ab Sandvik Materials Technology | Tube portion |
| CN112262297A (en) * | 2018-06-20 | 2021-01-22 | 山特维克材料技术公司 | Pipe section |
| US11143530B2 (en) | 2018-06-20 | 2021-10-12 | Ab Sandvik Materials Technology | Tube portion |
| CN112262297B (en) * | 2018-06-20 | 2022-04-26 | 山特维克材料技术公司 | Pipe section |
Also Published As
| Publication number | Publication date |
|---|---|
| SE9301633D0 (en) | 1993-05-12 |
| SE9301633L (en) | 1994-11-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |