Method and arrangement for determining concentration of at least two sample components in solution of at least three components

Abstract

An arrangement for determining concentration of at least two sample components in solution of at least three components comprises a refractometer as a first instrument for measuring refractive index data as a first quantity of the first sample component. In addition the arrangement comprises a second physical quantity measuring device for measuring second physical quantity as a second quantity data of the second sample component, such as a device for measuring conductivity. The second physical quantity is advantageously essentially independent on said refractive index, but is more strongly dependent on at least concentration of at least one second sample component of said solution. Further the arrangement comprises a data processing unit for determining said concentration of at least two sample components by using said refractive index data and second quantity data in an additive way after a variable substitution performed by said data processing unit on the refractive index data.

Claims

1. A method for determining concentration of at least two sample components in solution of at least three components, wherein the method comprises measuring: a refractive index data as a first quantity of the first sample component, and a second physical quantity as a second quantity data of at least one second sample component, where said second physical quantity is essentially independent of said refractive index, but is dependent on at least the concentration of at least one second sample component of said solution, and determining said concentration of at least two sample components by using said refractive index data and second quantity data in an additive way after a variable substitution is performed on the refractive index data.

2. The method of claim 1, wherein the variable substitution performed on the refractive index data is implemented by applying Lorenz-Lorentz transformation so to modify the refractive index data and enabling to provide a linear variable being additive sum of the effects of the individual component fractions for determination of said concentration of at least two sample components.

3. The method of claim 2, wherein temperature of the solution is measured and a temperature dependent compensation is applied to said measured refractive index data before applying said Lorentz-Lorenz transformation.

4. The method of claim 2, wherein the temperature correction is performed by determining at first a difference of Lorenz-Lorentz variable of pure water and Lorenz-Lorentz variable of the sample in question beforehand in order to provide a new temperature dependent variable and afterwards using said new variable for determining the temperature dependent compensation for the sample components.

5. The method of any of claims 2, wherein the Lorenz-Lorentz variable used to modify the refractive index data is: $\frac{n^2-1}{n^2+2}=\underset{i}{\overset{}{.Math.}}.Math.{}_i.Math.R_i$ where .sub.i, is partial density and R.sub.i is specific refractive index of the sample component in question.

6. The method of claim 1, wherein the second physical quantity is electrical conductivity of the solution, where said at least two sample components comprised by said solution is selected so that the electrical conductivity of the first component is essentially negligible in relation to the electrical conductivity of the second component of said at least two sample components.

7. The method of claim 6, wherein the relation between the concentration and electrical conductivity of the second component is: $=F.Math.\underset{i}{\overset{}{.Math.}}.Math..Math.z_i.Math..Math.{}_i.Math.c_i$ where F is Faraday constant, z.sub.i is ion charge, c.sub.i is ion concentration, and is specific electrical conductivity of the second component.

8. The method of claim 1, wherein said second quantity is at least one of the following: electrical conductivity, density, viscosity, X-ray absorption, ultrasound velocity, optical absorptions, colour determination, or particle counter.

9. The method of claim 1, wherein at least one component of said components is selected from a group of: salt, sugar, alkalinity, lignin, sulphidity, sodium sulphite, ammonia, ammonium nitrate, hydrogen peroxide, hydrogen chloride or hydrochloric acid, sulphide or sulphuric acid.

10. An arrangement for determining concentration of at least two sample components in solution of at least three components, wherein the arrangement comprises: a refractometer as a first instrument for measuring refractive index data as a first quantity of the first sample component, and a second physical quantity measuring device for measuring second physical quantity as a second quantity data of the second sample component, where said second physical quantity is essentially independent of said refractive index, but is dependent on at least the concentration of at least one second sample component of said solution, and a data processing unit for determining said concentration of at least two sample components by using said refractive index data and second quantity data in an additive way after a variable substitution performed by said data processing unit on the refractive index data.

11. The arrangement of claim 10, wherein the data processing unit is configured to perform variable substitution on the refractive index data implemented by applying Lorenz-Lorentz transformation and so to modify the refractive index data and to provide a variable being additive sum of the effects of the individual component fractions for determination of said concentration of at least two sample components.

12. The arrangement of claim 10, wherein the arrangement comprises also a thermometer for measuring temperature of the solution, whereupon the data processing unit is configured to apply a temperature dependent compensation to said measured refractive index data before applying said Lorentz-Lorenz transformation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which:

[0032] FIG. 1 illustrates a principle of an exemplary arrangement for determining concentration of at least two sample components in solution of at least three components according to an advantageous embodiment of the invention.

DETAILED DESCRIPTION

[0033] FIG. 1 illustrates an exemplary arrangemnt 100 for determining concentration of at least two sample components in solution of at least three components according to an advantageous embodiment of the invention. The arrangemnt 100 comprises advantageously at least one refractometer 102 as a first instrument for measuring refractive index data as a first quantity of the first sample component C1. In addition the arrangemnt 100 comprises advantageously at least one second physical quantity measuring device 103 for measuring second physical quantity as a second quantity data of the second sample component C2, where said second physical quantity is essentially independent on said refractive index, but is dependent on at least concentration of at least one second sample component of said solution. The arrangement may also comprise further additional second physical quantity measuring device 104 for measuring any additional second physical quantities. As an example the second physical quantity measuring device 103 may for example device for measuring conductivity of the second component C2, and the additional second physical quantity measuring device 104 may be for example device for measuring viscosity or density of the additional second component C3.

[0034] The arrangement comprises advantageously also a thermometer 106 for measuring temperature of the solution S (with components C1, C2, C3).

[0035] The arrangement also comprises advantageously a data processing unit 107 for determining said concentration of at least two sample components C1, C2, C3 by using said refractive index data and second quantity data in an additive way after a variable substitution performed by said data processing unit on the refractive index data. It is to be noted that the data processing unit 107 can be implemented in many ways, such as at least partly by a computer software product, or by calculation unit 101 and PLC (Programmable logic controller) unit 105, which controls for example the reading of different devices 102, 103, 104, 106 as well as the calculation unit 101.

[0036] The data processing unit 107 is advantageously configured to perform variable substitution on the refractive index data implemented by applying Lorenz-Lorentz transformation and so to modify the refractive index data and to provide a variable being additive sum of the effects of the individual component fractions for determination of said concentration of at least two sample components.

[0037] As can be seen in FIG. 1 as well as the description above, the exemplary principle of one embodiment of the invention is to use of at least two separate devices 102, 103, 104, one of which is an instrument measuring the refractive index of the sample solution S and the other some complementary measurement to be used in conjunction with the refractive index measurement, e.g. conductivity. The temperature measurement is gained from one of the instruments described previously or from a third separate instrument, such as thermometer 106. All of the instruments are placed as closely as possible in the process pipe 108 so as to get measurements of the same segment of the flow as possible. After the refractive index has been processed as per the description of the invention it is fed into a regular multivariate equation along with the complementary measurement result and the temperature to perform cross and temperature compensations on the variables. After calculation the concentrations of the two (or more) main components C1, C2, C3 in the solution S are provided via various means from the calculation unit 101.

[0038] The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the spirit and scope of the inventive thought and the following patent claims. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.