WO2003005012A1

WO2003005012A1 - Method for measuring of flow potential of a water solution and an apparatus for applying of method

Info

Publication number: WO2003005012A1
Application number: PCT/FI2001/000645
Authority: WO
Inventors: Petri Janhunen
Original assignee: Metso Field Systems Oy
Priority date: 2001-07-06
Filing date: 2001-07-06
Publication date: 2003-01-16

Abstract

The object of the invention is a method and an apparatus to measure flow potential of a water solution. In the method in accordance with the invention the water solution is transferred from a reservoir (7) under pressure through a pipe (9) and through a flow throttle (1, 5) and through another pipe (10) to another reservoir (8), in which the pressure is lower than in the first reservoir (7), and the difference in flow potential of the flowing solution and non-flowing solution is measured by electrodes (2, 6). The apparatus in accordance with the invention includes reservoirs (7, 8), pipes (9, 10) connecting the reservoirs, a flow throttle (1, 5) between the pipes, through which the water solution has been organized to be passed while transferred from reservoir (7) to another reservoir (8), electrodes (2, 6) measuring the flow potential of the solution, as well as a potentiometer measuring the difference in potential between the electrodes (2, 6).

Description

METHOD FOR MEASURING OF FLOW POTENTIAL OF A WATER SOLUTION AND AN APPARATUS FOR APPLYING OF METHOD

The present invention relates to a method for measuring of flow potential of a water solution. The present invention relates also to an apparatus for applying of method.

The determining of the surface charge created by dissolved and colloidal substances in water suspension is of great importance in order to understand properties of a water solution. Present methods in use for determining the state of charge of a water solution are based on titration that changes the color of solution by polyelectrolytes and color changing indicators or on determining of the flow potential in electrically insulated narrow space between a piston and a cylinder of a cylinder/piston combination.

The disadvantage of these methods is disturbing substances that have influence on the color changing reaction and thus the exact determining is difficult to obtain and the determining depends on the person. In the case of cylinder/piston combination mixing is imperfect and therefore the determining time is long. These determinings are not suitable for liquid solutions, which include particles of a size of fibres or greater but these liquid solutions must be filtrated before determining, which also creates a disadvantage.

The flow potential of water solutions is determined in various fields of industry and especially in paper industry, where the determining of properties of pulp solutions is of great importance in order to control the properties of paper. Furthermore, it is of importance to obtain the results of determining as soon as possible.

The purpose of the invention is to provide a method, in which the disadvantages of present methods are prevented. In particular, the purpose of the invention is to provide a method, by using which the determining may be accomplished regardless of the person automatically in a short period of time for all liquid solutions. Furthermore, the purpose of the invention is to provide an apparatus for applying of method, an apparatus of simple construction, which is easy to use and advantageous.

The purpose of the invention is accomplished by a method and apparatus, the characteristics of which are presented in the claims.

In the method according to the invention the liquid solution to be examined is transferred under pressure from one reservoir through a pipe and a flow throttle through another pipe to another reservoir in which the pressure is lower than in the first reservoir, and the potential difference between the flowing liquid solution and the non-flowing liquid solution is measured with electrodes. The difference in potential caused by the flow is measured with a potentiometer connected with electrodes. Using this method the flow potential of a water solution is quickly and simply determined. This method makes it possible to determine the flow potential measured from a water solution more quickly than when using earlier recognized methods and at the same time gives more reliable results than earlier. Thus it is possible to obtain one category quicker and more exact determining of concentration in determining the state of charge of a water solution. The method may be applied as an automatic method for determining. Thus costs due to personnel may be saved.

The method may be used to automatically determine flow potential of various water solutions. Especially the method is suitable to be applied in determining of properties of water solutions in paper industry. Determining may be carried out straight from the solution at the location thus the results are in use without delay.

In an advantageous application of the invention the difference in potential is measured between the electrode in the first reservoir and the electrode in the narrow space in the flow throttle. This kind of solution is simple and advantageous to realize.

In the second advantageous application of the invention the water solution to be examined is conducted from the reservoir by means of pressurized gas, such as compressed air or some other gas under pressure. It is advantageous and suitable for this purpose to use compressed air. In other applications also other gases under pressure may be used, such as nitrogen or some other gas suitable for the purpose.

In the third advantageous application of the invention the water solution to be examined is conducted from the reservoir by means of underpressure. Also by means of underpressure it is possible to create necessary flow reliably and exactly.

In the next advantageous application of the invention the water solution to be examined is conducted from the reservoir by means of a piston. Also by means of such construction a reliable and exact flow may be achieved.

The apparatus according to the invention includes reservoirs, pipes connecting the reservoirs, a flow throttle between the pipes, through which water solution is planned to flow while conducted from one reservoir to another, electrodes measuring the flow potential of water solution as well as a potentiometer measuring the difference in potential of the electrodes. Such an apparatus is simple in construction, advantageous to build and reliable in use.

In the next advantageous application of the invention the first electrode has been placed in the first reservoir and the second electrode in the flow throttle. The first electrode measures the water solution in the reservoir and the second electrode in the flow throttle measures the potential of the flowing solution. From the potentials measured by these electrodes the reliable difference in potential is achieved.

Next, the invention will be explained in more detail with reference to the accompanying drawing, which illustrates a principle figure from side of an apparatus according to the invention.

An apparatus in the figure includes two reservoirs 7, 8, pipes between them 9, 10, a flow throttle 1, 5, an electrode 6 in reservoir 7 and another electrode 2 in the flow throttle 1, 5 and a potentiometer 16 to measure the potential between these electrodes. The potentiometer 16 has been connected with electrodes by wires. The flow throttle has been constructed of two separate parts: part 1 with a canal, and closing part 5, movable with regard to part 1, and connected to a cylinder 4 which is moving it. The size of the space in the flow throttle is regulated with the cylinder e.g. the distance between the closing part 5 and the part 1. Canal 17 is connected to reservoir 7 in order to conduct a water solution to the canal. Furthermore, the apparatus includes an overpressure valve 12, which has been connected to a pump or equivalent to it by means of air hose 13 and with air hoses 14 and 15 to reservoirs 7 and 8. Reservoirs 7 and 8 are in this application cylindrical, but their shape may vary in different applications. The parts of the apparatus are made of materials not conducting electricity except of measuring electrodes. Measuring electrodes are made of material that doesn't corrode in solution. The apparatus has been placed on scales thus the solutions to be dosed may be exactly determined by measuring the increase in weight. Furthermore, the apparatus includes or to it has been connected an earlier recognized pneumatic apparatus, electronics and an analysing equipment of measuring signal and a computer. These are not closer illustrated.

The flow potential of a water solution is determined by applying the method according to the invention and using the apparatus according to the figure as follows: The water solution to be determined is directed to the reservoir 7 through the canal 17. Reservoirs 7 and 8 are at the moment under normal pressure. When the wanted amount of sample has been dosed to the reservoir 7, overpressure is obtained in reservoir 7 by directing compressed air through overpressure valve 12 and hose 14 to the reservoir. In overpressure valve compressed air is directed through line A, B. Correspondingly, overpressure valve line C, D is open through canal 15 to reservoir 8. Thus there is a difference in pressure between the reservoirs. This difference in pressure moves the water solution in reservoir 7 through the pipe 9 to the space in flow throttle and further through the pipe 10 to the reservoir 8. The space in the flow throttle is narrow and the size of it is regulated by regulating the distance of part 5 from the surface of part 1 by means of a cylinder 4. The flow creates a difference in potential between the electrode 6 in the reservoir and the electrode 2 in the flow throttle. The water solution in the reservoir 7 is used as zero potential for the measuring of flow potential. The difference in potential of flowing solution and not-flowing solution measured by the electrodes 2 and 6 is measured with the potentiometer 16. Information from the potentiometer is transferred to a computer and the results are reported as wanted. Measuring is automatic.

After enough water solution has been conducted from reservoir 7 to reservoir 8 in order to measure the flow potential the direction of flow is changed the other way round. Thus air pressure directed through overpressure valve 12 is conducted through line A, C and air hose 15 to reservoir 8 and there is an open contact from reservoir 7 to normal air pressure through air hose 14 of the overpressure valve 14 and line B, D. After the determining of the flow potential of solution has been accomplished reservoirs and the measuring space are rinsed. In cylinder 4 the space in flow throttle has been opened. Washing solution is directed through the canal 17 to the reservoir 7. When rinsing the wash solution is passed through open flow throttle between reservoirs 7, 8 by means of pressure difference created by means of compressed air. Rinsing is accomplished as many times as needed to achieve wanted purity level by non-charged calibration solution. The apparatus is emptied between the rinsing processes by opening the valve 11 in the pipe 10. Reservoirs and solution lines are washed automatically according to earlier chosen programme.

The invention is not limited to the presented advantageous application but it can vary within the frames of the idea of the invention formed in the claims.

Claims

1. A method for determining of flow potential of a water solution, characterize d in that the solution to be examined is passed under pressure from reservoir (7) through a pipe (9) through a flow throttle (1,5) and through another pipe (10) to another reservoir (8), in which the pressure is lower than in the first reservoir (7), and that the difference in potential of flowing solution and not-flowing solution is measured by means of electrodes (2, 6).

2. A method in accordance with claim 1, characterized in that the difference in potential is measured between the electrode (6) in the reservoir (7) and the electrode (2) in the space in the flow throttle.

3. A method in accordance with claim 1 or 2, characterized in that the solution to be examined is conducted from the reservoir (7) by means of pressurized gas, such as compressed air or other gas under pressure or by underpressure.

4. A method in accordance with claims 1 or 2, characterized in that the solution to be examined is conducted from the reservoir (7) by means of underpressure.

5. A method in accordance with claims 1 or 2, characterized in that the solution to be examined is conducted from the reservoir (7) by means of a piston.

6. An apparatus to determine flow potential of a water solution, characteri- z e d in that the apparatus includes reservoirs (1, 8), pipes (9, 10) connecting the reservoirs, a flow throttle (1,5) between the pipes, through which the water solution has been organized to be passed while transferred from reservoir (7) to another reservoir (8), electrodes (2, 6) measuring the flow potential of the solution as well as a potentiometer (16) to measure the difference in potential between the electrodes (2, 6).

7. An apparatus in accordance with claim 6, characterized in that the other electrode (2) has been placed in the flow throttle (1,5) and the other electrode (6) has been placed in the reservoir (7).

8. An apparatus in accordance with claim 6, characterized in that the apparatus has been place on scales.